Using AIDS Initial Assessment questionnaire (AIA) data from 353 injection drug users (IDUs) newly admitted to methadone maintenance (MM), three dimensions of injection risk behavior (“sharing with sexual partner,”“sharing with others,”and“new needle use”) were identified. Among IDUs who continued to inject drugs at 1 year, men retained in treatment obtained lower scores on the“sharing with others”scale than men not retained, even when controlling for initial scale scores and injection frequency. Associations between retention in MM and changes in sexual risk were examined using two AIA measures of sexual risk behavior (“number of IDU sexual partners”and“relative frequency of unprotected vaginal intercourse”). Controlling for injection frequency, prior sexual risk, and age, there was no difference in sexual risk for men retained in treatment versus those not retained. Among women, those who stayed in MM for 1 year reported significantly fewer IDU partners.