Abstract From 1977 to 1981, the intravenous use of a pentazocine/tripelennamine combination (T's and Blues) has become a major drug abuse problem in the city of St. Louis, Missouri, U.S.A. There has been a continuous increase in the involvement of these drugs in (a) sudden and violent deaths (62 homicides, 7 fatal intoxications), (b) emergency room visits (137 in 1980), (c) admissions to drug treatment programs (7.7% in 1978 up to 64% in 1981), and (d) police laboratory cases (100 in 1977–1978 up to 700 in 1981). Initial popularity of the drugs was related to the decline in the quality of street heroin (2.5% in 1977 reduced to 0.5% by 1979) and the lack of strict legal controls. Serious adverse reactions include clonic-tonic seizures and pulmonary foreign body granulomatosis. Ethanol and diazepam were present in 53% and 10% of T's and Blues medical examiner's cases, respectively ( n = 70). Addicts are usually black males, 20–30 years old, from impoverished areas of the city. The drugs are available to the illicit trade through theft or diversion from legitimate sources.