Substance abusers are at particular risk for becoming infected with, and for spreading, a number of serious communicable diseases. The value of substance abuse treatment in helping to reduce the associated risk behaviors for these diseases is the focus of this technical report. This analysis examines the risk behaviors of injection drug use and sex exchange among clients in the National Treatment Improvement Evaluation Study (NTIES). It describes the characteristics and drug use patterns of clients who practiced these behaviors before they entered treatment, the types of services they received during treatment, and the changes in these behaviors following treatment. A statistical model is employed to predict which clients will practice these behaviors in the follow-up period. Overall the findings supported the hypothesis that substance abuse treatment reduces or even prevents the practice of the high risk behaviors of injection drug use or sex exchange. The findings nonetheless showed strong relationships between the clients' pre-treatment risk behaviors and their post-treatment behaviors and outcomes. It concludes with a summary and recommendations for substance abuse treatment research, practice, and policy. (Contains 69 references.) (JDM)