To investigate the role of treatment modality in relapse prevention treatment. 32 cocaine-dependent subjects were randomly assigned by cohorts to group-based relapse prevention (G-RP) or individually based RP (I-RP). The two RP formats were identical in content, consisting of 12 outpatient treatment sessions over a 2-month period immediately following hospitalization. The proportion of subjects providing cocaine-free urines at the end of RP treatment did not differ between formats: however, G-RP subjects reported using cocaine on significantly fewer days during treatment, and experiencing fewer cocaine-related problems than did I-RP subjects. Follow-up data collected at 12 and 24 weeks' posttreatment revealed no significant differences between RP formats on any cocaine-use outcome measures. Regardless of therapy format, RP treatment was related to statistically significant and sustained improvements in other areas of psychosocial functioning, including addiction severity, coping, and craving for cocaine. The overall findings suggest that the efficacy of relapse prevention training is not limited by therapy format.