What Is Multidistrict Litigation (MDL)?

Official sources: U.S. Judicial Panel on Multidistrict Litigation (JPML) | Administrative Office of the U.S. Courts | 28 U.S.C. § 1407 | Federal Rules of Civil Procedure

Legal information reviewed: August 2026

What is multidistrict litigation?

Multidistrict litigation is a way for federal courts to manage many civil lawsuits that involve similar factual questions.

Instead of allowing dozens, hundreds, or thousands of related federal cases to conduct the same discovery and argue the same pretrial issues before different judges, the Judicial Panel on Multidistrict Litigation can transfer the cases to one federal district court for coordinated or consolidated pretrial proceedings.

Federal law allows transfer when doing so will:

• Serve the convenience of parties and witnesses.
• Promote the just and efficient conduct of the cases.
• Help avoid duplicative discovery and inconsistent pretrial rulings. (law.cornell.edu)

The judge who receives the cases is commonly called the transferee judge.

What does MDL stand for?

MDL stands for multidistrict litigation.

The term describes a federal procedure created under 28 U.S.C. § 1407.

An individual proceeding is generally identified by a docket number, such as:

• MDL 2873 — AFFF firefighting foam litigation.
• MDL 3004 — Paraquat litigation.
• MDL 3026 — Preterm infant nutrition products litigation.
• MDL 3047 — Social media adolescent addiction litigation.
• MDL 3094 — GLP-1 gastrointestinal injury litigation.

An MDL number identifies the coordinated federal proceeding. It does not mean the underlying lawsuits have become one case.

Who decides whether an MDL is created?

The U.S. Judicial Panel on Multidistrict Litigation, commonly called the JPML, decides whether federal lawsuits should be centralized.

The Panel is made up of seven sitting federal judges appointed by the Chief Justice of the United States. No two members may come from the same federal judicial circuit. (jpml.uscourts.gov)

The JPML considers questions including:

• Do the lawsuits involve common factual issues?
• Would centralization make the litigation more efficient?
• Would transfer benefit parties and witnesses?
• Which federal district is the best location?
• Which judge should oversee the coordinated proceedings?

The Panel can grant or deny a request for centralization.

How is an MDL created?

The process generally begins when a party asks the JPML to transfer related federal lawsuits into one coordinated proceeding.

The Panel reviews the motion and responses from other parties.

It may also hold oral argument during one of its scheduled hearing sessions.

If the JPML concludes that centralization is appropriate, it issues a transfer order identifying:

• The litigation.
• The federal district receiving the cases.
• The judge who will oversee the MDL.
• The general factual issues supporting centralization.

Additional related federal cases can later be transferred into the MDL as tag-along actions.

What types of cases can become MDLs?

MDLs can involve many kinds of federal civil litigation.

Examples include:

• Defective medical devices.
• Dangerous drugs.
• Consumer products.
• Data breaches.
• Antitrust cases.
• Securities litigation.
• Air disasters.
• Environmental contamination.
• Intellectual property disputes.
• Marketing and sales practices.

Product-liability mass torts receive significant attention because they can involve thousands of injured plaintiffs, but MDLs are not limited to personal-injury cases.

For example, the federal judiciary reported that new MDLs created during fiscal year 2025 included data-breach, intellectual-property, antitrust, product-liability, marketing-and-sales-practices, and air-disaster proceedings. (uscourts.gov)

Is an MDL the same as a class action?

No.

This is one of the most important distinctions.

MDL

In multidistrict litigation:

• Plaintiffs generally retain individual lawsuits.
• Each plaintiff may have different injuries and damages.
• Cases are coordinated primarily for pretrial proceedings.
• Individual cases may settle or proceed differently.

Class action

In a class action:

• One or more representative plaintiffs seek to represent a defined group.
• A court must certify the class.
• Common issues generally determine the claims of class members.
• A judgment or approved settlement may bind qualifying class members.

An MDL can contain thousands of individual plaintiffs without ever becoming a class action.

Is an MDL the same as a mass tort?

No, although the terms often overlap.

A mass tort describes a situation in which many people allege similar injuries from the same or related products, exposures, or conduct.

An MDL is a federal court procedure for coordinating related lawsuits.

A mass tort may become an MDL if enough similar federal cases exist and the JPML determines centralization is appropriate.

But not every mass tort becomes an MDL.

For example, plaintiffs sought to create a federal Video Game Addiction Products Liability MDL in 2024, but the JPML denied centralization. Those cases therefore continued separately.

What happens after cases enter an MDL?

Once an MDL is created, the transferee judge takes responsibility for managing common pretrial proceedings.

That can include:

• Discovery.
• Document production.
• Depositions.
• Expert evidence.
• Motions to dismiss.
• Summary judgment motions.
• Scientific or causation issues.
• Plaintiff questionnaires or fact sheets.
• Case-selection procedures.
• Settlement discussions.
• Bellwether preparation.

The goal is to avoid having many different federal judges repeatedly decide the same pretrial questions.

What is discovery in an MDL?

Discovery is the process in which the parties exchange evidence and obtain information relevant to the lawsuits.

Because MDLs may involve thousands of cases, discovery can be enormous.

It may include:

• Internal company documents.
• Emails.
• Scientific studies.
• Regulatory communications.
• Medical records.
• Product records.
• Corporate testimony.
• Expert reports.
• Plaintiff-specific records.

The transferee judge typically establishes procedures for managing this evidence across the entire litigation.

What is a Plaintiff Fact Sheet?

A Plaintiff Fact Sheet, or PFS, is a standardized questionnaire used in many MDLs to gather information about individual plaintiffs.

A fact sheet may ask about:

• Product use.
• Exposure history.
• Injury or diagnosis.
• Medical treatment.
• Employment.
• Other possible causes of injury.
• Damages.

Using a standardized form makes it easier to collect comparable information from thousands of plaintiffs.

Some MDLs use different names, such as a Plaintiff Assessment Questionnaire.

Failure to complete required plaintiff forms can sometimes lead to sanctions or dismissal.

What is a bellwether trial?

A bellwether trial is a test trial involving an individual case selected from a larger group of similar lawsuits.

Bellwethers can help the parties evaluate:

• Scientific evidence.
• Legal arguments.
• Witness credibility.
• Jury reactions.
• Potential case values.
• Settlement risk.

The JPML itself highlights scholarship on the role of bellwether trials in multidistrict litigation. (jpml.uscourts.gov)

A bellwether verdict generally does not automatically decide every other case in the MDL.

Who chooses bellwether cases?

The process varies by MDL.

Cases may be selected by:

• Plaintiffs' leadership.
• Defendants.
• The judge.
• A combination of those groups.
• Random or structured selection procedures.

Courts often try to identify cases that can provide useful information about recurring issues in the litigation.

A case may appear representative but later prove unsuitable because of unique medical, factual, jurisdictional, or evidentiary issues.

Does a bellwether verdict determine what everyone gets paid?

No.

A bellwether verdict applies to the individual case that was tried.

It may influence settlement negotiations by showing how a jury responds to the evidence, but it does not create an automatic payout schedule for every plaintiff.

For example, one plaintiff may have:

• More severe injuries.
• Longer exposure.
• Stronger product identification.
• Different medical history.
• Different state law.

Those differences can affect individual outcomes.

Can an MDL judge dismiss cases?

Yes.

Although cases are coordinated for pretrial proceedings, the transferee judge can issue major rulings that affect individual cases or large groups of cases.

Those rulings may involve:

• Pleading requirements.
• Statutes of limitation.
• Expert evidence.
• Causation.
• Product identification.
• Federal preemption.
• Failure to comply with discovery obligations.

An MDL does not guarantee that a case will reach settlement or trial.

The Paraquat MDL, for example, experienced significant dismissals after the court excluded causation expert testimony in its first bellwether group.

Can an MDL judge decide scientific issues?

A judge does not personally decide scientific truth, but the court determines whether expert testimony meets federal evidentiary requirements.

This can be critical in cases alleging that a product or exposure caused a disease.

Courts may evaluate:

• Epidemiology.
• Toxicology.
• Mechanistic evidence.
• Exposure science.
• Medical causation.
• Methodology used by experts.

If a plaintiff lacks admissible expert testimony on an issue they must prove, the claim may be dismissed before trial.

What happens if the parties reach a settlement?

Mass-tort MDLs often create conditions for large-scale settlements because the parties have already developed:

• Common evidence.
• Plaintiff-specific data.
• Scientific records.
• Bellwether results.
• Litigation risk assessments.

A settlement may use:

• Eligibility criteria.
• Injury categories.
• Settlement tiers.
• Point systems.
• Settlement matrices.
• Extraordinary-injury funds.
• Individual review procedures.

Not every MDL settles globally.

And even when a settlement program exists, some plaintiffs may choose not to participate if the agreement allows opt-outs.

Is an MDL settlement mandatory?

Not automatically.

Whether a settlement binds an individual plaintiff depends on the structure of the settlement and the plaintiff's participation.

In many personal-injury MDLs, plaintiffs retain individual claims and decide whether to accept an offered settlement.

Some settlements may establish participation thresholds before defendants are required to proceed.

The rules must be evaluated based on the specific settlement agreement.

What is a settlement matrix?

A settlement matrix is a framework that may be used to organize compensation among many claims.

It can consider factors such as:

• Type of injury.
• Severity.
• Duration.
• Surgery.
• Medical treatment.
• Age.
• Exposure.
• Other risk factors.

Not every MDL uses a settlement matrix.

And a matrix does not necessarily mean every plaintiff with the same diagnosis receives the same amount.

What happens if an MDL does not settle?

Cases that remain unresolved after coordinated pretrial proceedings may eventually need to return to the federal districts where they originated.

Under 28 U.S.C. § 1407, transferred actions are generally supposed to be remanded to their original districts at or before the conclusion of coordinated pretrial proceedings unless they were otherwise resolved. (law.cornell.edu)

The Supreme Court reinforced that principle in Lexecon Inc. v. Milberg Weiss, holding that an MDL transferee court cannot simply use another transfer statute to assign a transferred case to itself for trial over the statutory remand requirement. (law.cornell.edu)

Does every MDL case get sent back for trial?

No.

Many cases never reach remand because they are:

• Settled.
• Dismissed.
• Voluntarily withdrawn.
• Resolved through pretrial rulings.
• Otherwise terminated.

Only unresolved transferred cases potentially require remand for further proceedings or trial.

Can cases be filed directly into an MDL?

Sometimes.

Some MDL judges allow direct filing, which permits plaintiffs to file directly in the transferee district rather than first filing elsewhere and waiting for a JPML transfer.

Direct filing can reduce administrative burden.

But direct filing does not necessarily determine which state's law applies or where an unresolved case would ultimately be tried. Those questions depend on the case-management orders and applicable law.

What is a tag-along action?

A tag-along action is a newly filed federal lawsuit that involves factual questions similar to cases already centralized in an MDL.

The JPML can transfer qualifying tag-along cases into the existing MDL.

This is how an MDL may continue growing after the original transfer order.

The Panel's 2026 procedural rules govern transfer practice and tag-along proceedings. (jpml.uscourts.gov)

How long does an MDL last?

There is no standard timeline.

An MDL may last:

• Months.
• Several years.
• More than a decade.

The timeline depends on factors such as:

• Number of cases.
• Complexity of evidence.
• Scientific disputes.
• Number of defendants.
• Appeals.
• Bellwether trials.
• Settlement negotiations.
• Bankruptcy proceedings.
• Regulatory developments.

Large product-liability MDLs can remain active long after initial settlements begin.

How can I tell whether an MDL is still active?

The most authoritative source is the U.S. Judicial Panel on Multidistrict Litigation.

The JPML publishes reports listing active MDLs and updates them on the first business day of each month. (jpml.uscourts.gov)

Those reports can show information such as:

• MDL number.
• Litigation name.
• Transferee district.
• Judge.
• Number of pending actions.
• Historical number of actions.

The individual federal district court overseeing the MDL may also maintain an official litigation page with orders, calendars, and case-management materials.

Does being in an MDL mean your lawsuit is strong?

No.

Centralization is an administrative decision about efficient case management.

The JPML does not decide when creating an MDL that:

• The defendant is liable.
• The product caused the alleged injury.
• Plaintiffs will win.
• A settlement will occur.
• Every claim is valid.

Cases can later be dismissed for many reasons.

Does creating an MDL mean a settlement is coming?

No.

MDLs can make coordinated settlement discussions easier, but the creation of an MDL does not guarantee a settlement.

Some MDLs:

• Settle extensively.
• Produce individual trials.
• Experience major dismissals.
• Continue for years.
• End with different outcomes for different groups of plaintiffs.

The existence of an MDL should therefore never be treated as proof that compensation is guaranteed.

Common misconceptions

Myth: An MDL combines thousands of lawsuits into one giant class action where everyone gets the same result.

Reality: MDL centralization coordinates related federal lawsuits primarily for pretrial proceedings. Individual plaintiffs generally retain separate cases, injuries, evidence, and damages. Unless claims settle or are otherwise resolved, transferred cases generally remain subject to eventual remand to their original districts. (law.cornell.edu)

Why this matters

MDLs sit behind many of the largest mass-tort lawsuits consumers hear about, but the term is frequently misunderstood.

An MDL is not a lawsuit itself, not proof that plaintiffs will win, and not a class action.

It is a case-management system.

Its purpose is to avoid making hundreds of federal judges repeatedly supervise the same document discovery, hear the same expert arguments, and decide the same pretrial questions.

For an individual plaintiff, the important questions remain personal:

What happened to you? What evidence supports your claim? Can the product be identified? Can causation be established? What damages occurred? And how will the MDL's rulings or settlement process affect your individual case?