To estimate the lifetime prevalence of drug and alcohol use and its sociodemographic determinants and to investigate opinions towards drug use in Spain, we examined a representative nation-wide sample of 2495 adult Spaniards, males and females, aged 18 y or older, selected by a multistaged random strategy during 1989. Information was obtained by at-home interviews using a structured closed questionnaire. Participants were asked for their lifetime prevalence of use of cannabis, sedatives and sleeping pills, alcohol, amphetamines, inhalants, cocaine and heroin, as well as for their sociodemographic characteristics and their opinions towards drug use. Alcohol had the highest lifetime prevalence of consumption (55.7%), followed by cannabis (12.3%), sedatives and sleeping pills (12.0%), amphetamines (4.3%), cocaine (3.0%), inhalants (0.8%) and heroin (0.6%). Being male, young, separated or divorced, and unemployed were the main determinants of alcohol and drug use. A higher use of illicit drugs was also observed in the higher socio-economic groups. Regular use of any drug was considered a risky health habit by more than 80% of the sample. We conclude that the consumption of drugs and alcohol is a rather extended habit in Spain. Drug users tend to share some common sociodemographic characteristics (being male, young, separated or divorced, and unemployed) which may help target intervention programs.