Several recent decisions by the US Supreme Court have strengthened the ability of federal courts to consider medical testimony regarding injuries associated with exposure to toxic substances. Judges are expected to examine the basis of all expert testimony before it is introduced at trial to ensure that it meets the same standards of intellectual rigor that professionals use outside the courtroom. However, courts have been inconsistent in measuring this testimony against the standards of medical practice, especially when courts consider testimony that is not supported by clinical trials or epidemiological studies. A number of courts have required standards for expert testimony that exceed those that physicians use in ordinary clinical decision making. In this article, we illustrate such inconsistencies across federal courts by contrasting different decisions in cases involving similar facts and expert testimony. We argue that there may be good reason to require a standard of admissibility that exceeds the standards of ordinary clinical decision making, but such requirements are not faithful to the mandate of the Supreme Court. Courts with especially demanding standards are misled if they believe that they are fairly representing medical practice. Physicians should respond by correcting courts' misinterpretations of medical practice and assisting in the development of legal standards that encourage thoughtful and informed consideration of medical testimony by judges and juries.