This study examined outcome variables for 160 opiate injection drug users (IDUs) who entered methadone maintenance between baseline and 6-month follow-up. Outcome variables of interest included drug use, productivity, and HIV risk behaviors. Participants were recruited through street outreach in Denver, CO, from 2000 through 2004 using targeted sampling. The sample was primarily men, White (48%), averaged 39 years of age, and had been injecting drugs for an average of nearly 20 years. Significant improvements were found in univariate tests. Logistic regression revealed that spending more time in treatment was a significant predictor of positive outcomes on drug use and HIV risk behaviors. The results underscore the importance of retaining IDUs in methadone maintenance to maximize their treatment success. Results from this study show that time in treatment can affect many aspects of the participant's life in a positive way, including reduction of HIV risk.