New drugs are subjected to three phases of human testing, beyond animal testing, before they can be approved for marketing in the United States. Included must be at least some randomized clinical trials (RCTs), conducted to test both the efficacy and safety of the drug when given at a particular dosage for a particular indication.1 Generally, between 500 and 3,000 patients are exposed to a drug prior to marketing. Clearly, such premarketing testing does not provide absolute assurance of safety, as demonstrated by the frequent postmarketing discoveries of adverse effects.2,3 This has led to greater emphasis on postmarketing surveillance.2-7 Yet, the presumption persists that premarketing testing assures efficacy, ie, that an approved drug does tend to produce its intended effect. A recent series of articles questions this presumption, however, raising concerns about whether studies of efficacy should also be included as part of postmarketing research8-10 and,