Plaintiffs appeal as of right from an order of the Wayne County Circuit Court granting partial summary judgment in favor of defendants. This is a multiple-plaintiff, multiple-*66defendant products liability action involving a widely-distributed prescription drug. The trial judge ruled that each plaintiff, in order to state a cause of action sufficient to withstand a motion for summary judgment, must identify in the complaint which of the defendants allegedly manufactured the specific product which caused his or her harm. Those plaintiffs who could not name the particular defendant whose product harmed them had summary judgment of no cause of action entered against them. Those plaintiffs who named a particular defendant had their claims against all defendants other than the named defendant dismissed.
This action was commenced on September 17, 1974, when plaintiffs filed a complaint alleging that defendants are jointly and severally liable for damages on the theories of negligence, breach of express and implied warranties, fraud and conspiracy. The complaint was amended 14 times. Specifically, the complaint alleged that defendants were negligent in failing to perform adequate tests on the synthetic estrogens known as dienestrol, diethylstilbestrol or diethylstilbestrol diproprionate (hereinafter DES),1 in distributing DES and promoting it for the prevention of miscarriages in pregnant women when they knew, or in exercise of due care would have discovered, that it presented a danger to the child in útero, and in failing to warn consumers of the dangers inherent in use of DES to prevent miscarriages. The complaint further alleged that DES was defective in that it was not effective in the prevention of miscarriage, in that *67it caused the development of cancerous or precancerous lesions in the vaginas of females whose mothers consumed DES while pregnant, and in that the product carried inadequate warnings of the danger presented to unborn children whose mothers consumed DES while pregnant. The female plaintiffs alleged that they developed cancerous or precancerous conditions as a result of the consumption of DES by their mothers while plaintiffs were in útero. The male plaintiffs are husbands of the female plaintiffs.
Plaintiffs’ complaint also alleged that the defendants named therein constituted all of the known manufacturers of DES whose products were distributed in Michigan during the relevant time period, that one or more of the named defendants caused the harm to each of the plaintiffs, but that some plaintiffs were unable to discover which particular defendant caused their harm because of the destruction of medical and pharmacy records. Plaintiffs further alleged that the inability to name the individual defendant should not bar recovery, in that defendants were jointly and severally liable for the harm to plaintiffs because all defendants acted wrongfully and only the drug companies named in the suit could have caused plaintiffs’ harm. The complaint further alleged that defendants were collectively liable for plaintiffs’ harm.
Discovery and other proceedings, for the most part irrelevant to this appeal, consumed more than two years and produced a voluminous record. On February 1, 1977, defendants filed a motion for partial summary judgment alleging: (1) that they were entitled under GCR 1963, 117.2(1) to summary judgment of no cause of action agáinst all plaintiffs who were unable to name the manufac*68turer of the particular product which caused their injury; (2) that plaintiffs’ allegations of collective, industry-wide liability did not state a cause of action cognizable under the laws of the State of Michigan, thus requiring summary judgment as to that claim under GCR 1963, 117.2(1); and (3) that there existed no genuine issue as to any material fact regarding the conspiracy or concert of action count and that defendants were entitled to summary judgment as a matter of law under GCR 1963, 117.2(3). Defendants’ motion was supported by affidavits which stated that more than 300 manufacturers were listed in standard reference works as offering DES for sale during the relevant time period. In opposition to the motion, plaintiffs produced affidavits to the effect that the list of defendants was "inclusive of’ manufacturers whose products were being distributed in Michigan during the relevant time period.
On May 16, 1977, the trial court issued its opinion granting summary judgment of no cause of action: (1) for all defendants against those plaintiffs unable to allege specifically the defendant whose product harmed them; (2) for all defendants, other than the defendant named, against those plaintiffs who alleged that a particular defendant caused their harm; and (3) for all defendants against all plaintiffs on the claim of collective liability. All judgments were granted pursuant to GCR 1963, 117.2(1).
On August 25, 1977, plaintiffs filed their 14th amended complaint, in which 70 plaintiffs alleged that a particular defendant caused their harm. On the same date, the trial court entered a final order granting partial summary judgment for defendants in accordance with its opinion of May 16, 1977. On September 7, 1977, claim of appeal was filed in this Court on behalf of 182 plaintiffs.
*69Plaintiffs argue on appeal that the trial court erred, first, in holding that each plaintiff must allege which defendant produced the drug which harmed her in order to state a cause of action and, second, in holding that in their allegations of collective liability plaintiffs failed to state a claim upon which relief may be granted. In reviewing plaintiffs’ claims of error, we must keep in mind certain rules. We note first of all that a motion for summary judgment under GCR 1963, 117.2(1) merely tests the legal sufficiency of the pleadings. Todd v Biglow, 51 Mich App 346; 214 NW2d 733 (1974). The test is whether plaintiffs’ claim as pled is so clearly unenforceable as a matter of law that no factual development can possibly justify a right to recovery. Crowther v Ross Chemical & Manufacturing Co, 42 Mich App 426; 202 NW2d 577 (1972). Further, we must bear in mind that a motion under Rule 117.2(1) does not test plaintiffs’ ability to prove their allegations. Lompre v Venetjoki, 76 Mich App 521; 257 NW2d 151 (1977). The trial court in ruling on the motion must accept as true all well pleaded facts in the complaint. Stewart v Troutt, 73 Mich App 378; 251 NW2d 594 (1977). On review, this Court must apply the same rules. Lincoln Park Detention Officers v Lincoln Park, 76 Mich App 358; 256 NW2d 593 (1977).
The remedy afforded consumers as against sellers and manufacturers of defective goods, which has been termed "products liability”, has been described as "not [a] statutory, but essentially a judicial development which the courts should be free to develop further”. Parish v B F Goodrich Co, 395 Mich 271; 235 NW2d 570 (1975). See also Moning v Alfono, 400 Mich 425; 254 NW2d 759 (1977). It has roots in both contract and tort law, but is distinct from both. See discussion in Cova v *70Harley Davidson Motor Co, 26 Mich App 602; 182 NW2d 800 (1970). In Michigan, two theories of recovery are recognized in the area of products liability: negligence and breach of implied warranty. Johnson v Chrysler Corp, 74 Mich App 532; 254 NW2d 569 (1977). Under a negligence theory, the plaintiff must establish the traditional common-law elements of duty, breach, damage and causation. See Moning v Alfono, supra. To establish breach of implied warranty, the plaintiff must show that a defect in the product, attributable to the manufacturer, caused his injuries. Smith v E R Squibb & Sons, Inc, 405 Mich 79; 273 NW2d 476 (1979).
It is self-evident that the defective product must be shown to have come from defendant rather than some other manufacturer, for if defendant has neither acted negligently nor breached his implied warranty he can incur no liability. See Anno: Products Liability: Necessity and sufficiency of identiñcation of defendant as manufacturer or seller of product alleged to have caused injury, 51 ALR3d 1344. In the ordinary case, the plaintiff knows (or believes he knows) the identity of the sole tortfeasor, and the proofs are directed toward establishing the wrongful conduct of the tortfeasor and the causal connection between that conduct and the harm to plaintiff. Occasionally plaintiff alleges that one or more tortfeasors have acted wrongfully and that one or the other, or both, caused his injury. See, for example, Jordan v Whiting Corp, 396 Mich 145; 240 NW2d 468 (1976) (the estate of crane repairman electrocuted by crane sues the manufacturer of the crane parts, the assembler of the crane and the installer of the wiring), Elsasser v American Motors Corp, 81 Mich App 379; 265 NW2d 339 (1978) (a plaintiff injured *71by fire resulting from a collision which ruptured the gas tank of his car sues the driver of the car which struck his and the manufacturer of his car). In such a case plaintiff seeks to prove wrongful conduct on the part of all defendants and resulting harm to himself. A defendant in such a case, in addition to denying that his conduct was wrongful, often defends on grounds that his negligence or his defective product has not been shown to be a proximate cause of plaintiff’s injury. See the discussion in Dooms v Stewart Bolling & Co, 68 Mich App 5; 241 NW2d 738 (1976).
Those cases in which plaintiff alleges that his injury was caused by more than one tortfeasor may be variously classified. Prosser divides so-called joint torts according to the rationale for imposing joint and several liability into eight classes, including those involving concerted action and cases of alternative liability.2 The claims asserted in the case at bar fall into two categories: concerted action and alternative liability.3 Plaintiffs allege that all defendants acted wrongfully in producing and marketing a defective product, and that each plaintiff was injured by the product of one or the other defendant. They also allege that all defendants acted wrongfully, and one (but only one) of the defendants caused the harm to each individual plaintiff, therefore, they are alternatively liable. Plaintiffs also allege that all defendants, acting in concert, caused the marketing of *72DES, and that this concerted activity is the cause of plaintiffs’ injuries and that all defendants, having acted together to cause all the harm, are jointly and severally liable therefor.
Defendants argue in their brief on appeal that permitting plaintiffs to proceed to trial on their concert of action theory is without precedent and is tantamount to imposing liability on an innocent manufacturer for the actions of his fellows. This argument misperceives the nature of plaintiffs’ claim. It is well-established that if two or more persons engage negligently in concerted activity, and as a result plaintiff is injured, all are liable even though only one directly caused the injury. McCoy v DeLiefde, 376 Mich 198, 205; 135 NW2d 916 (1965) (opinion of Souris, J.). Liability is imposed on all because all have joined in breaching their duty of care to plaintiff, and he was injured as a result of that breach. Plaintiffs in their complaint allege that defendants acted in concert to produce and market ineffective and dangerous products, without adequate testing and without adequate warnings. These allegations are sufficient to state a cause of action, and summary judgment as to the concerted activity claim was improper, McCoy v DeLiefde, supra.
Defendants also argue that there is no evidence that defendants acted in concert in producing and marketing DES, and claim that no such proof exists. It is sufficient to say that a motion for summary judgment under GCR 1963, 117.2(1) tests only the sufficiency of the pleadings. Lompre v Venetjoki, supra. Resolution of this disputed fact question must await trial, McCoy v DeLiefde, supra.4
*73The concert of action claim is a true joint tort, and once the fact of a tortfeasor’s liability is established, its extent is clear: he is jointly and severally liable for the entire amount of damages, although he may be entitled to contribution from his fellow tortfeasors. See Prosser, Joint Torts and Several Liability, 25 Cal L Rev 413 (1937), Caldwell v Fox, 394 Mich 401; 231 NW2d 46 (1975). Although a joint tortfeasor may (and usually does) dispute the fact of liability, he may not dispute the extent thereof. He may seek to show that only his codefendant, and not he, acted wrongfully, but he may not seek to show that his fellow tortfeasor caused all or the greater portion of the damage and should therefore pay a greater share. See Sexton v American Aggregates, 60 Mich App 524; 231 NW2d 449 (1975). Even if defendant caused no harm himself, he is liable for the harm caused by his fellows because all acted jointly. Benson v Ross, 143 Mich 452; 106 NW 1120 (1906).
The alternative liability theory, on the other hand, involves not a joint tort, but rather, involves independent acts by two or more tortfeasors, all of whom have acted wrongfully, but only one of whom has injured plaintiff. Joint and several liability is imposed, not because all are responsible for the damage, but because it is impossible to tell which one is responsible. Rather than deny the innocent plaintiff his recovery because he cannot prove which of two or more wrongdoers injured him, the courts impose joint liability on all wrongdoers. In cases of alternative liability, a defendant is free to absolve himself of blame and cast the entire burden on his fellows, even if it be shown that he acted wrongfully, but that defendant must beár the burden of proving that his wrongful act was not the cause of plaintiffs injury. See Sum*74mers v Tice, 33 Cal 2d 80; 199 P2d 1; 5 ALR2d 91 (1948). Prosser has described the situation typified by Summers, supra, as "clearly established double fault and alternative liability”. Prosser, Torts (3d ed), § 41, p 247. This apt description helps to distinguish these cases from the situation in which there is but a single act of negligence by one of multiple defendants, but it is not clear which defendant committed that act. See Anno: Liability of Several Persons Guilty of Acts One of Which Alone Caused Injury, in Absence of Showing as to Whose Act Was the Cause, 5 ALR2d 98, 100. Joint and several liability is imposed only on those who are clearly shown to be wrongdoers.
Although no cases directly on point appear in Michigan, the shifting of the burden of disproving causation once defendant’s wrongful conduct has been established appears in other contexts in Michigan law. In Snider v Bob Thibodeau Ford, Inc, 42 Mich App 708; 202 NW2d 727 (1972), for example, a consumer brought an action against both the manufacturer of his automobile and the dealer who had repaired the brakes which allegedly failed and caused his accident. The trial court in that case directed a verdict for the manufacturer (Ford Motor Company), and plaintiff appealed. Rejecting Ford Motor Company’s argument that the directed verdict was proper because plaintiffs proofs were insufficient to show which defendant was responsible for the defect, if any, this Court said:
"Were a jury to decide that the wrong to Snider had been established, the question to which of two possible tortfeasors — Ford or Thibodeau — liability should be assigned does not pose an issue of conjectural cause.
"True, the burden of proving which of two possible wrongdoers is responsible is generally assigned to the *75plaintiff. The courts have, however, shown a willingness to consider special circumstances when allocating the burden of proof. This accords with the general view that the placing of that burden is 'merely a question of policy and fairness based on experience in the different situations’.” (Footnote omitted.) 42 Mich App, at 718.
In Holloway v General Motors Corp (On Rehearing), 403 Mich 614; 271 NW2d 777 (1978), the Supreme Court held that plaintiff need not show the precise nature of the defect in defendant’s product so long as he carries his burden of establishing by a preponderance of the evidence that some defect attributable to defendant caused his injury, saying in a footnote:
"In a somewhat analogous situation, the rule is that a plaintiff need not prove which person among alternative negligent tortfeasors caused his injury. See Summers v Tice, 33 Cal 2d 80; 199 P2d 1 (1948); Prosser, supra § 41, pp 243-244.” Holloway, supra, fn 15, 625.
Also instructive is the analysis presented in Maddux v Donaldson, 362 Mich 425; 108 NW2d 33; 100 ALR2d 1 (1961), which involved successive automobile collisions. The Court held that where plaintiff was unable to prove what portion of the damages were caused by each collision because of the circumstances of the accident, the burden of uncertainty should fall on the wrongdoers, who would be jointly and severally liable for all plaintiff’s damages.
"Is it better, as we asked heretofore, that a plaintiff, injured through no fault of his own, take nothing, rather than that a tort-feasor pay no more than his theoretical share of the damages accruing out of a confused situation which his wrong has helped to create?” Maddux, supra, 435.
*76The Court answered the question thus posed by holding that, if injustice is inevitable, the burden should fall on the wrongdoer rather than on the innocent plaintiff. With this conclusion we agree.5
In the case before us, as in Maddux, supra, the problem is essentially one of apportionment of damages among proven wrongdoers. Plaintiffs must establish that they suffered a certain amount of damages at the hands of defendants, all of whom are tortfeasors. Should plaintiffs succeed in establishing that defendants are alternatively liable for this amount of damages, defendants are left to apportion the damages among themselves. Each defendant is free to present proofs absolving itself from liability as to any particular plaintiff or as to all plaintiffs. Defendants are also free to implead any third party who they believe liable for all or part of the damages.
Plaintiffs in the case at bar bear a heavy, perhaps (as defendants contend) an insuperable, burden of proof, one made even more difficult by the number of defendants and by the length of time between the ingestion of the allegedly defective drug and the appearance of the damages allegedly caused thereby. They must establish by a preponderance of the evidence that each defendant breached its duty of care in producing the product, that the harm to each plaintiff was the result of ingestion of DES by her mother, and that one or more of the named defendants manufactured the DES so ingested.6 Each plaintiff must carry her *77burden as to these defendants in order to recover. Should plaintiffs fail to carry their burden as to any or all defendants, they will suffer the consequences. We will not add to plaintiffs’ burden by requiring them to apportion damages among the wrongdoers in order to recover.
In so holding, we adopt no new theory of law, despite the urging of plaintiffs that we adopt the "enterprise liability” theory of products liability.7 We simply follow precedent established by the courts of Michigan and other states in finding that the trial court imposed too heavy a burden on plaintiffs by requiring them to plead more facts than are necessary to state a cause of action in products liability. Accord, Sindell v Abbott Laboratories, 85 Cal App 3d 1; 149 Cal Rptr 138 (1978). Cf. McCrerry v Eli Lilly & Co, 87 Cal App 3d 77; 150 Cal Rptr 730 (1978).
Reversed and remanded for further proceedings consistent with this opinion.
Bronson, J., concurred.Defendants assert in their brief that only diethylstilbestrol is properly denominated DBS, the other compounds being chemically distinct from DES. We express no opinion on the similarities or differences among the various substances, but simply adopt the designation "DES” for convenience.
The other classes are: vicarious liability; common duty; concurrent causation of a single, indivisible result, which neither would have caused alone; concurrent causation of a single, indivisible result, which either would have caused alone; successive injuries; damage of the same kind, which it is difficult to apportion; and acts innocent in themselves which together cause damage. Prosser, Joint Torts and Several Liability, 25 Cal L Rev 413, 429-442 (1937).
See analysis in Sheiner, DES and a Proposed Theory of Enterprise Liability, 46 Fordham L Rev 963, 978-995 (1978).
For an excellent discussion of the proof problems which are likely to be presented in this case, see Sheiner, supra, note 3, 983-985.
Defendants seek to distinguish prior alternative liability cases by reason of the fact that the tortious acts occurred within a brief time span. We find this argument unpersuasive. It hardly comports with the notions of fairness which underlies the adoption of joint and several liability for independent tortfeasors to hold that a tortfeasor who continues his wrongful conduct over a period of years will be absolved of responsibility for his acts as a reward for his persistence in wrongdoing.
Those plaintiffs who believe they are able to identify the defen*77dant who injured them may wish to take the less perilous route of pursuing their cause of action against a sole tortfeasor rather than seeking to establish the alternative liability of all defendants. If so, they will no doubt seek to amend their pleadings accordingly. Those who have already amended their complaint to allege a sole tortfeasor may either amend to allege joint and alternative liability or stand on the most recent amendment.
See Sheiner, supra, note 3, for a discussion of this proposed theory.