In 1987 a study was made of the consumption of dependency-producing substances in the urban population of Colombia. For this purpose the prevalence survey method was applied to a representative sample of 2,800 individuals between the ages of 12 and 64. The descriptive analysis was supplemented by the exploration of causal associations and measurement of the strength of such associations by means of the prevalence ratio coupled with calculation of the degree of statistical significance. The study included three substances whose consumption is socially accepted--alcohol, tobacco, and tranquilizers--and another three considered to be illicit--basuco (coca-paste), cocaine, and marijuana. Alcohol and tobacco were the two drugs most used by both sexes (560 and 297 per 1,000 subjects studied, respectively). Tranquilizers, the only one of the drugs in the study that was used more by women, ranked third (60 per 1,000). Reported in much smaller proportions were marijuana (11 per 1,000), basuco (6 per 1,000), and cocaine (3 per 1,000). It may be noted that the consumption of basuco has recently reached a level double that of cocaine. Analysis of the use and abuse of these substances by age, marital status, socioeconomic situation, and other variables indicates that the prevalence of consumption is higher in the medium age groups, that unmarried persons are at excess risk compared with those who are married, that men from the upper classes tend to use cocaine and marijuana, and that both sexes in the lower classes use basuco as the drug of preference. Differences in suicide rates between users and nonusers were statistically significant in the population aged 15 to 54, and it was determined that the substances of greatest risk, generally for women, were basuco and marijuana.