Jason Daubert and Eric Schuller (P) are minor children born with serious birth defects. They and their parents sued respondent in California state court, alleging that the birth defects had been caused by the mothers' ingestion of Bendectin, a prescription anti-nausea drug marketed by respondent. D removed the suits to federal court on diversity grounds. After extensive discovery, D moved for summary judgment, contending that Bendectin does not cause birth defects in humans and that petitioners would be unable to come forward with any admissible evidence that it does. D introduced expert opinions claiming that there was no causal link between Benedectin and birth defects. P countered with declarations from eight medical experts, supporting the existence of such a link. These experts had concluded that Bendectin can cause birth defects. Their conclusions were based on “in vitro” (test tube) and “in vivo” (live) animal studies that found a link between Bendectin and malformations; pharmacological studies of the chemical structure of Bendectin that purported to show similarities between the structure of the drug and that of other substances known to cause birth defects; and the “reanalysis” of previously published epidemiological (human statistical) studies. The District Court stated that scientific evidence is admissible only if the principle upon which it is based is “‘sufficiently established to have general acceptance in the field to which it belongs.’ Given the vast body of epidemiological data concerning Bendectin, the court held, expert opinion which is not based on epidemiological evidence is not admissible to establish causation. Thus, the animal-cell studies, live-animal studies, and chemical-structure analyses on which petitioners had relied could not raise by themselves a reasonably disputable jury issue regarding causation. Ibid. Petitioners' epidemiological analyses, based as they were on recalculations of data in previously published studies that had found no causal link between the drug and birth defects, were ruled to be inadmissible because they had not been published or subjected to peer review. D's motion for summary judgment was granted, and the action was dismissed. The United States Court of Appeals for the Ninth Circuit affirmed. citing Frye v. United States, 54 App. D.C. 46, 47, 293 F. 1013, 1014 (1923), the court stated that expert opinion based on a scientific technique is inadmissible unless the technique is “generally accepted” as reliable in the relevant scientific community. The court declared that expert opinion based on a methodology that diverges “significantly from the procedures accepted by recognized authorities in the field . . . cannot be shown to be ‘generally accepted as a reliable technique.’ The Supreme Court granted review.