We conducted a cross-sectional study to assess sexual and drug use risk in 161 children and youth in street circumstances in Porto Alegre, Brazil. Median age was 14 and 79% were male. Overall, 59% reported ever having had sex; a significantly higher proportion of males (66%) compared to females (30%). Overall, 39% reported illicit drug use in the last year, and only 1.2% reported injection drug use. In multivariate analyses, correlates of unsafe sex included younger age of sexual debut, and having a steady sex partner. Independent correlates of illicit drug use included lack of family contact, increased hours in the street daily, having had an HIV test, and older age. A high proportion of children and youth in street circumstances reported high risk sex and drug exposures, confirming their vulnerability to HIV/STD. Services Centers, such as where this research was carried out, offer an opportunity for interventions.