Longitudinal trajectories for HIV risk were examined over 5 years following treatment among 1,393 patients who participated in the nationwide Drug Abuse Treatment Outcome Studies. Both injection drug use and sexual risk behavior declined over time, with most of the decline occurring between intake and the first-year follow-up. However, results of the application of growth mixture models for both sets of trajectories indicated that a subgroup of individuals reverted to a high-risk behavior over time, with a higher level of risk at the 5-year follow-up than their original risk level at intake. Of clients who were engaged in regular injection drug use at intake, 76% continued to inject drug at a moderate-stable or increased rate during the 5-year follow-up. (Contains 6 tables and 2 figures.)