Each sample was tested by immunoassay for amphetamines, barbiturates, benzodiazepines, cocaine metabolite, cannabinoids, methaqualone, opiates, phencyclidine, and propoxyphene. Positive screen results were confirmed by gas chromatography-mass spectroscopy (GC-MS). In addition, each sample was tested for flunitrazepam metabolites and gamma-hydroxybutyrate (GHB) by GC-MS and for ethanol by GC-flame ionization detection. Over a 26-month period, 1,179 samples were collected and analyzed from 49 states, Puerto Rico, and the District of Columbia. Of the 1,179 samples, 468 were negative for all substances tested; 451 were positive for ethanol, 218 for cannabinoids, 97 for benzoylecgonine, 97 for benzodiazepines, 51 for amphetamines, 48 for GHB, 25 for opiates, 17 for propoxyphene, and 12 for barbiturates. No samples were identified as positive for phencyclidine or methaqualone. In addition, 35 percent of drug-positive samples contained multiple drugs. The authors conclude that, with respect to alleged sexual assault cases, the prevalence of ethanol is very high, followed by cannabinoids, cocaine, benzodiazepines, amphetamines, and GHB. The study raises the concern of illicit and licit drug use in sexual assault cases and suggests the need to test for a range of drugs in such cases. 24 references, 2 tables, and 4 figures