A pilot study concluded that drugs could be rapidly and accurately identified by gas chromatography-mass spectrometry, with the resulting information being of value in the clinical handling of drug overdoses. The service has continued to be of use at Suburban Hospital since 1972. Although the major user of the drug identification service is Suburban Hospital itself, increasing numbers of samples have been received from other hospitals. The most readily available samples that can be obtained for drug identification are blood, urine, and gastric contents. Two mass spectrometric approaches have been used. The method used routinely at Suburban involves chemical ionization mass spectrometry. The backup method is the standard electron ionization mass spectrometric technique. Caseload data suggest that the rapid growth in the use of the service from 1973 to 1976 has ceased, and a steady caseload of between 500 and 600 cases annually has been reached. About 90 different drugs have been encountered since the service began, with by far the most commonly encountered substance being caffeine (25 percent of cases). The most commonly abused lethal drug is secobarbital. Diazepam (Valium is the trade name) is the most commonly implicated tranquilizer. Tabular and graphic data along with four references are provided.