Kaufman (plaintiff) was diagnosed with cervical cancer at age 18. Kaufman sued manufacturers of diethylstilbestrol (DES), a medication taken by pregnant women to prevent miscarriage, alleging that her cancer resulted from her mother taking DES while pregnant. Because Kaufman did not know which manufacturer made the DES her mother ingested, Kaufman sued some 147 pharmaceutical companies who manufactured and marketed DES, including Eli Lilly & Co. (Lilly) (defendant). Among various theories, Kaufman claimed a concerted action theory of liability, alleging that the defendants had conspired to obtain approval of DES without adequately testing it. Kaufman was one of 15 plaintiffs who brought similar actions in the First Department of the Supreme Court of New York. The first of the 15 cases to be tried was Bichler v. Lilly & Co., 55 N.Y.2d 571 (1982). The Bichler jury found in favor of the plaintiff and answered seven special interrogatories in the plaintiff’s favor. One of the jury’s findings was that Lilly was liable under a theory of concerted action. The appellate division affirmed. After the Bichler decision, Kaufman moved for partial summary judgment granting collateral estoppel effect to six of the findings made by the Bichler jury, including the finding that Lilly was liable under a theory of concerted action. The appellate division affirmed but granted Lilly leave to appeal.