OBJECTIVES: To assess the demographic characteristics, psychiatric symptoms, substance use patterns, and sexual risk behaviors in a sample of club drug users to identify factors associated with unprotected sex during the 12 months prior to the interview. METHODS: This cross-sectional study employed the targeted sampling and ethnographic mapping approaches via face-to-face interviews conducted at bars and electronic music festivals using an adapted, semi-structured version of the Global Appraisal of Individual Needs questionnaire. The sample comprised 240 male and female young adults who had used ecstasy and/or LSD in the 90 days prior to the interview and who were not receiving treatment for alcohol or drug abuse. RESULTS: Of the 240 subjects selected (mean age: 22.9±4.5 years), 57.9% were men; of the male subjects, 52.5% reported having had unprotected sex in the previous 12 months. Of the total sample, 63.33% reported having had unprotected sex. Multivariate regression analysis showed that anal sex (PR = 1.26; 95% confidence interval (CI): 1.044-1.543; p = 0.017) and the use of alcohol/drugs to make sex last longer (PR = 1.430; 95% CI: 1.181-1.732; p<0.001) are associated with unprotected sex. CONCLUSIONS: The implementation of intervention strategies aimed at reducing sexually risky behaviors should take into consideration the specific characteristics of drug users and should include the development of safer sex negotiation skills.