Epidemiological and analytical laboratory records concerning living drivers suspected of driving under the influence of drug (DUID) during the 13 years period ranging from 1982 to 1994 were examined. This study included 641 records. 551 men (86%) and 90 women (14%). The average age of the drivers was 27 +/- 7 years (n = 636, minimum 18 and maximum 74) and the 18-30 interval age range was overrepresented (80%) in this population sample. A traffic accident had occurred in 254 (40%) of the records, 273 (43%) drivers were suspected of DUID during police controls and 95 (15%) drivers were suspected of DUID because of their erratic driving. One or more psychoactive drugs were found in 92.8% of the samples. In these records, cannabinoids were found in 57%, opiates in 36%, ethanol in 36%, benzodiazepines in 15%, cocaine in 11%, methadone in 10% and amphetamines in 4%. The majority (58%) of cases presented two or more drugs in biological samples, thus indicating a high incidence of potential interactions between drugs. This observation was specially relevant for methadone and methaqualone. We conclude that police suspicion about drivers under influence highly correlated with positive results for drug analyses in biological samples.