What Is a Mass Tort? MDL vs. Class Action Explained

“Mass tort” shows up constantly in law firm advertising, but it isn’t a formal legal category with its own set of court rules. It’s a description of a situation — a large number of people harmed by the same product, drug or contamination source — and in federal court that situation is almost always managed through a specific procedural tool: multidistrict litigation, or MDL.

Understanding what an MDL actually is, and how it differs from a class action, is the difference between reading a “lawsuit update” article usefully and being misled by one — because the two structures answer the most important question, whose decision is it whether your case settles, in opposite ways.

Quick answer: A class action is one lawsuit that resolves an entire group’s claims at once, with one settlement or verdict binding everyone in the class (unless they opt out). An MDL — the structure almost all modern drug, medical device and mass-contamination litigation actually uses — instead consolidates thousands of individual lawsuits before one judge for coordinated pretrial work. Each plaintiff keeps their own case. A small number of bellwether trials test how juries value the claims, and that evidence is what usually pushes the parties toward a global settlement — but until one is reached and finalized, “the lawsuit” isn’t one thing with one outcome for everyone in it.

Why “Mass Tort” Isn’t a Legal Term

Courts and statutes talk about multidistrict litigation (28 U.S.C. § 1407), class actions (Federal Rule of Civil Procedure 23), and consolidated state-court coordination — in California, a Judicial Council Coordination Proceeding, or JCCP. “Mass tort” is the umbrella marketing term for all of it. That looseness is exactly why two different litigations both described as “the [product] mass tort” can be in completely different legal postures — one might have a finalized settlement fund paying claims today, another might not have a single bellwether trial scheduled yet. Major utility-caused wildfire litigation is a concrete current example of state-court coordination rather than a federal MDL — see our guide to wildfire liability claims against a utility for how that litigation is actually structured.

A third centralizing structure exists outside product-liability mass torts entirely: when an organization facing thousands of individual claims — most commonly in institutional sexual abuse litigation — files for Chapter 11 bankruptcy, a court-ordered channeling injunction can redirect every current and future claim into a single settlement trust, in a manner functionally similar to an MDL’s consolidation but built on bankruptcy law rather than 28 U.S.C. § 1407. See our guide to how Boy Scouts and Catholic diocese abuse settlement trusts actually pay claims for how that mechanism works and how it differs from both the MDL and class-action structures described below. That mechanism met its biggest legal test yet in the Purdue Pharma opioid bankruptcy, where the U.S. Supreme Court itself struck down a plan provision releasing non-debtor third parties without claimants’ consent — see our guide to the Purdue Pharma opioid settlement and what individual victims actually get for how that ruling forced a complete renegotiation.

MDL vs. Class Action: The Actual Difference

	Class Action	MDL
Number of lawsuits	One, on behalf of a defined group	Thousands, each its own case
Who decides to settle	Class representatives and class counsel, subject to court approval of the whole deal	Each plaintiff and their own attorney, individually
Can you opt out	Usually yes, before a deadline	Not applicable — you were never grouped into one judgment to begin with
Typical use in injury litigation	Often for pure economic-loss or one-time-event harms	Standard structure for drug, medical device and contamination personal injury claims
What ends it	Court approves a settlement or the case is tried to verdict	Individual settlements, remand to home courts for trial, or a global settlement most — not necessarily all — plaintiffs join

The practical consequence: in an MDL, no single event legally “resolves your case” the way a class action’s final approval hearing does. A global settlement in an MDL is really a very large private agreement that a very large share of individual plaintiffs’ attorneys are recommending their own clients accept — which is why participation percentages and opt-out counts matter so much to whether one holds together.

How an MDL Actually Moves

1. Consolidation. The Judicial Panel on Multidistrict Litigation (JPML), a standing panel of federal judges, decides that similar lawsuits filed around the country share enough common questions to justify centralizing them, and picks one district court and judge to manage pretrial proceedings. Consolidation is a decision, not a formality — the JPML has, for example, twice declined to centralize sex trafficking lawsuits against hotel chains, reasoning that each case turns on its own specific property, staff and facts rather than shared questions; see our guide to suing a hotel for trafficking for what litigating without that consolidation actually looks like in practice.
2. Leadership and case census. The judge appoints a plaintiffs’ leadership committee (and sometimes a liaison for the defense), and the parties establish how many cases actually exist — this number is reported publicly and changes monthly as new cases are filed or transferred in.
3. Coordinated discovery and expert admissibility. The parties litigate shared factual and scientific questions once, rather than thousands of times — this is usually where the most time passes, often years, and where Daubert or Rule 702 hearings decide whether the plaintiffs’ causation experts can testify at all. The Ozempic and Wegovy GLP-1 litigation is currently sitting at exactly this stage, with a Rule 702 hearing scheduled for September 2026 that could decide whether the case ever reaches a bellwether trial.
4. Bellwether selection and trial. A small, negotiated set of representative cases goes to trial (or is prepared to). Verdicts here are not binding precedent for other plaintiffs, but they are the real-world data point both sides use to price the claims. A single bellwether can also produce a genuinely mixed result that resolves less than it appears to — see our guide to the Bard PowerPort litigation for a first bellwether trial that ended in a defense verdict on some claims and a hung jury on the central one.
5. Settlement, or remand. Either a global settlement framework emerges — usually requiring a claims administrator, eligibility criteria, and often a special master to help negotiate or allocate — or cases are sent back (“remanded”) to the federal district where each was originally filed for individual trial.

Reading “Litigation Status” Correctly

A few habits separate an accurate read from a misleading one:

• A settlement “announcement” is not a finalized, funded settlement. Large mass-tort settlements are frequently conditioned on a minimum percentage of eligible plaintiffs agreeing to participate — if that threshold isn’t hit, the deal can be renegotiated or can fall apart entirely. “Reached a $X billion settlement” and “settlement final, checks going out” are different facts, and content (including this site’s) needs to say which one is true as of its publish date.
• A verdict in one bellwether trial doesn’t tell you what your case is worth. It’s one jury’s answer on one set of facts. Multiple bellwethers with different outcomes for the same defendant is normal, not a sign something is wrong with the process.
• Check whether the deadline described is for filing a new claim, or for an existing claimant to opt in or opt out of a specific settlement. These are different deadlines with different consequences, and mass-tort marketing content sometimes blurs them to create urgency.
• The most fact-checkable sources are the court itself, not law firm marketing. The federal district court hosting the MDL typically maintains an official page for it; the docket itself is public on CourtListener or PACER; the JPML publishes a periodic report of every pending MDL and its case count. State-court coordinated proceedings (like a California JCCP) have their own court-maintained dockets.
• A settlement’s own claims-administration process can fail in more than one direction at once. The NFL concussion settlement is a genuinely instructive example: a biased testing formula wrongly excluded legitimate claimants for years, while a separate fraud scheme got tens of millions in improper claims approved — two opposite integrity failures inside the same fund.
• An objection to a settlement can fail for reasons that have nothing to do with whether the objection was right. See our guide to the East Palestine train derailment settlement for objectors whose appeal over inadequate future-harm compensation was dismissed for missing an appeal bond deadline — a procedural failure, not a ruling on the underlying argument.
• “Dismissed” is not always the end of the story. An expert-exclusion ruling that ends a litigation at the district court can still be appealed and reversed. See our guide to the Tylenol autism and ADHD litigation for a federal appeals court reviving more than 500 cases in 2026 after reversing the very expert exclusion that had dismissed them in 2024 — and note that the reversal itself was still only a ruling on admissibility, not a finding that the underlying allegation is true.

What to Do If You Think You Have a Claim

An MDL’s existence doesn’t create your claim — your injury and your state’s filing deadline do. Our mass tort eligibility screener checks your situation against the litigations covered on this site and points you to the right guide, if one applies. Beyond that:

1. Don’t wait to find an attorney who handles the specific litigation. Evaluating whether your facts fit is exactly what a consultation is for, and it’s free in this area of practice — see our guide to personal injury lawyer fees for how contingency arrangements work.
2. Confirm your own state’s filing deadline separately from anything you read about the MDL. An MDL doesn’t extend or replace your statute of limitations — it only determines which court a timely-filed case is coordinated in.
3. Be skeptical of any service asking for money upfront to “register” your claim. Court-appointed claims administrators don’t charge claimants to determine eligibility.
4. Expect the timeline to be long. Years between filing and any payment is normal for this kind of litigation, not a sign your claim was mishandled.
5. Once a settlement actually exists, know that eligibility and payment are separate steps. See our guide to filing a claim in a class action or mass tort settlement for the claim form, documentation and deadline that actually connect the two.

Sources & Further Reading

• 28 U.S.C. § 1407 — the federal statute authorizing multidistrict litigation and creating the Judicial Panel on Multidistrict Litigation
• Federal Rule of Civil Procedure 23 — the class action rule, for contrast with how an MDL is structured
• Judicial Panel on Multidistrict Litigation (jpml.uscourts.gov) — publishes a periodic report listing every active MDL and its pending case count
• Federal Judicial Center, Manual for Complex Litigation, Fourth — the standard reference federal judges use for managing MDLs and other complex cases
• See our current-status guides to active litigations for what this looks like in practice: the talcum powder ovarian cancer settlement, the social media youth mental health litigation, the Camp Lejeune water contamination claims, the Roundup/glyphosate litigation, the Depo-Provera meningioma litigation, the hair relaxer cancer litigation, the AFFF firefighting foam litigation, the paraquat and Parkinson’s disease litigation, and the hernia mesh litigation for an example of four separate manufacturers each running their own MDL over related products, the IVC filter litigation for two manufacturers with two entirely different outcomes so far — one resolved through confidential settlements, the other still working through a mixed bellwether record — and the NEC baby formula litigation for a single MDL where federal bellwethers have been dismissed before reaching a jury while parallel state-court cases against the same defendant have produced nine-figure verdicts, and, where a death results, our guide to wrongful death from a defective product or mass tort
• One category of injury claim skips this entire structure by statute — see our guide to vaccine injury claims and the VICP for the federal no-fault program a covered vaccine injury must go through first