The association between cocaine use (crack and injection cocaine) and risky behaviors for human immunodeficiency virus (HIV) infection was investigated among participants in a multi-site study at drug treatment and non-drug treatment sites in Worcester, Massachusetts. Cocaine use was more prevalent among young, African-American men. Compared to heroin injectors cocaine injectors had higher risk injection and sexual behaviors. Among non-injectors, crack users were more likely to have multiple partners and receive money or drugs for sex. Cocaine use, either injected or smoked as crack, should be considered a high risk behavior for HIV infection.