This article describes data from 4,111 males and 4,085 females participating in 10 HIV/AIDS service demonstration projects. The sample was diverse in age, gender, ethnicity, HIV status, and risk for HIV transmission. Logistic regression was used to determine the attributes that best predict substance abuse. Males who were younger; HIV positive; homeless; involved in the criminal justice system; had a sexually transmitted disease (STD); engaged in survival sex; and participated in risky sex with men, women, and drug injectors were most likely to have a substance abuse history. For females, the same predictors were significant, with the exception of having an STD. Odds ratios as high as 6 to 1 were associated with the predictors. Information about sexual and other risk factors also was highly predictive of substance abuse issues among youth.