Tramadol HCl, marketed as Ultram in the USA, was introduced as a non-scheduled drug in April 1995 based on the assumption that the risk of abuse was sufficiently low to warrant a non-scheduled status. However, approval was contingent upon the development of an innovative proactive surveillance program, to be overseen by an independent steering committee, which would detect unexpectedly high levels of abuse. The postmarketing surveillance program consisted of systematic collection and scientific evaluation of reports of suspected abuse in high-risk populations surveyed through an extensive key informant network of drug abuse specialists and all spontaneous reports of abuse received through the FDA MedWatch system. Methods to estimate the number of patients prescribed tramadol were also developed. Monthly rates of abuse were calculated as an index of the risk-benefit ratio (i.e., abuse cases per 100,000 patients prescribed the drug). The data for the 3 years since the drug was introduced show that the reported rate of abuse has been low. Although a period of experimentation seemed to occur in the first 18 months after its introduction--which reached a peak rate of approximately two cases per 100,000 patients exposed--during the 2 year period prior to June 1998, the reported rate of abuse has significantly (P = 0.011) declined, reaching levels of less than one case per 100,000 patients in the last 18 months. The overwhelming majority of abuse cases (97%) have been found to occur among individuals with a history of substance abuse and the abuse has been confined to isolated pockets around the country-notably none of which have significant populations of street drug abusers. Thus, the data support the decision not to schedule tramadol and, furthermore, suggest that a proactive post-marketing surveillance program can be successfully developed to effectively monitor abuse of new medications.