This article provides a review of various types of literature on gender differences among substance abusers. The authors begin this literature review by summarizing the literature on the differing treatment needs of men and women. The authors continue with a review of the empirically based literature on gender differences in background characteristics of substance users. They conclude with a review of treatment outcome studies. This review provides a context for identifying the gaps in the literature and identifies a research agenda that will help improve treatment services for women in both community-based and prison settings. (Contains 1 table.)