The aim of this study was to analyze a possible relationship between first experience with drugs and delinquency among adolescents in conflict with the law. In 2006, a cross-sectional study was conducted in facilities of the State Foundation for the Well-being of Minors (FEBEM), with a total occupancy of 312. The sample consisted of 150 male adolescents (48% of the total population) aged 12 to 21, confined for the first time in FEBEM detention centers for socio-educational rehabilitation in Sertãozinho and Ribeirão Preto, São Paulo State, Brazil. An individual questionnaire with closed questions was used. Results showed high rates of first-time alcohol, cigarette, and marijuana use, occurring concomitantly around 12 years. The most common offenses were robbery (44.7%), followed by drug traffic (29.4%), and theft (9.3%), occurring around 13. The data show that drug use occurs prior to offenses.