This study examined the association between sexual identity and use of alcohol and other drugs (AOD) among college undergraduate students. A survey regarding AOD use was administered to a random sample of 3607 undergraduate students. The sample included 65 self-identified lesbian or bisexual (LB) women and 54 self-identified gay or bisexual (GB) men. Multivariate logistic regression indicated that while alcohol use did not differ for LB and heterosexual women, LB women were significantly more likely to experience certain AOD-related consequences, smoke cigarettes, and use marijuana, ecstasy, and other drugs. GB men were significantly less likely than heterosexual men to drink heavily but were more likely to use some drugs. These findings provide evidence that sexual identity is an important predictor of AOD use among undergraduate students. These findings support the need for continued research and intervention efforts that target LGB collegians.