The survey was conducted in 1997 with 689 students aged 14 to 21 years at a high school in the city of Sao Paulo, Brazil. Drug use and sexual behavior were investigated through an anonymous, self-filled questionnaire. Sexual behavior of drug users and non-users was compared regarding history of complete sexual intercourse, age at first sexual intercourse, use of condoms, sexual intercourse with sex workers, and prostitution. Study results showed 53 percent of the students used drugs. Alcohol and marijuana consumption were related to a younger age at first sexual intercourse, non-use of condoms, sexual intercourse with sex workers, and prostitution. Sexual risk behavior was higher in alcohol and marijuana users than in cocaine and crack users. Inhalant and hallucinogen use association with sexual risk behavior were stronger than that found for cocaine and weaker than that for alcohol and marijuana users. The strong association between use of inhalants and prostitution merits specific studies. More frequent use of alcohol and higher number of drugs used were related to lower age at first sexual intercourse. Sexual intercourse with sex workers was associated with the use of all types of drugs and was stronger among those who used a higher number of different drugs. Analyzing all variables together, males showed more sexual risk behavior than females. The finding of lower condom use and more sexual intercourse with sex workers among drug users is alarming because of the association of two risk behaviors. It suggests that prevention campaigns should review their approach in regard to this specific target population (male drug users, especially alcohol and marijuana users) since these individuals more frequently show sexual risk behavior. 8 tables, 23 references