The extent of drug use among drivers suspected of driving under the influence of alcohol and/or drugs in Finland was studied. All blood samples submitted to the laboratory during 1 week in two study periods, in 1979 (n = 298) and 1993 (n = 332), were analyzed for alcohol and psychotropic drugs. Drugs classified as hazardous to traffic safety were detected in 7.0% of the samples in 1979 and 26.8% in 1993. Benzodiazepines were the most frequently found drugs in both years: 6.0% of the cases in 1979 and 22.9% in 1993. Illegal drugs were found in 4% of the cases in 1993. Of the samples tested, 296 in 1979 and 317 in 1993 were from drivers suspected of driving under the influence of alcohol only. In 1979 every fourteenth and in 1993 every fourth of these suspected drunken drivers had drugs in their blood. Drugs, other than alcohol, were found six times more often than expected by the police. The results indicate that the trend of drug use, multidrug use and drug abuse is increasing among cases suspected of driving under the influence of alcohol/drugs.