Relationships between sexual orientation and a wide range of substance use and problem variables were examined based on data from the 2000 National Alcohol Survey. Lesbians, bisexuals, and heterosexually identified women who report same-sex partners were compared to exclusively heterosexual women in relation to alcohol consumption, use of tobacco and other drugs, bar-going, alcohol-related problems, and past substance abuse treatment. Substance use patterns were complex and varied between sexual orientation groups. These differences underscore the importance of developing lesbian- and bisexual-sensitive prevention and treatment services and of including measures of sexual orientation identity and behavior in population-based surveys.