Objective: Contingency management (CM) treatments are usually applied individually for drug abstinence, but CM can also be targeted toward health behaviors and implemented in groups. This study evaluated effects of a group-based CM intervention that focused on reinforcing health behaviors. Method: HIV-positive patients with cocaine or opioid use disorders (n = 170) were randomized to weekly CM or 12-step (TS) groups for 24 weeks (mean attendance was 10.8 plus or minus 8.1 sessions for CM participants and 9.0 [plus or minus] 6.9 session for TS participants). During the treatment period, both groups received compensation for attendance ($10 per session) and submission of urine samples (about $2 per sample). In addition, participants received $25 for submitting samples and completing evaluations at Months 1, 3, 6, 9, and 12; 65-75 of the 81 participants assigned to TS and 71-80 of the 89 participants assigned to CM completed these evaluations. During the treatment period, patients in the CM group received chances to win prizes contingent upon completing health activities and submitting substance-free specimens (M = $260, SD = $267). Results: Mean attendance was 10.8 [plus or minus] 8.1 sessions for CM participants and 9.0 plus or minus 6.9 sessions for TS participants. CM participants submitted a significantly greater number of consecutive drug-free specimens than did TS participants (5.2 plus or minus 6.0 vs. 3.7 plus or minus 5.6), but proportions of negative samples did not differ between groups during treatment or at follow-up evaluations. From pre- to posttreatment, CM participants showed greater reductions in viral loads and HIV-risk behaviors than did TS participants, but these effects were not maintained throughout the follow-up period. Conclusions: These data suggest the efficacy of group-based CM for HIV-positive substance abusers, but more research is needed to extend the long-term benefits. (Contains 4 figures and 2 tables.)