OBJECTIVES: This article describes a sample of 160 adults selected to participate in a randomized controlled trial conducted at a specialized outpatient clinic for cannabis users in Brazil. It correlates consumption with several measures of marijuana use, comparing it with other samples. METHODS: Instruments used were the Composite International Diagnostic Interview (CIDI) and Wender Utah Rating Scale for screening and demographic data interviews, and the ASI, time-line follow back (TLFB), Marijuana Withdrawal and Marijuana Problem Scales, and Diagnostic and Statistical Manual of Mental Disorders (DSM-III-R) Checklist for cannabis dependence. RESULTS: Participants in the study were mostly single, white men; their mean age was 32.3 years. They had a mean of 15.6 years of formal education and 61.6% worked. The cohort started using marijuana at a mean age of 16.5 years and developed daily use by a mean age of 21 years. Subjects in the sample had used marijuana for a mean of 15 years. They used it for 92.2% of the 90 days prior to the interview and smoked a mean of 1.99 marijuana cigarettes per day during this period. Individuals in the group had experimented with other drugs, especially cocaine. CONCLUSIONS: Marijuana users in this sample matched the profiles of those investigated elsewhere, although they reported fewer symptoms of dependence. Marijuana users should be considered independently in substance abuse programs, because they require specific attention and treatment. Broader epidemiological studies should be conducted to determine the extent of marijuana use within the Brazilian population.