['Contingency management (CM) is efficacious in reducing drug use. This study examined whether CM also reduces human immunodeficiency virus (HIV) risk behaviors and if these effects are mediated by longest duration of abstinence achieved during treatment.', 'Data were analyzed from a subset of participants in a combined data set of three published randomized controlled trials of CM treatments.', 'A community-based methadone maintenance clinic.', 'One-hundred and sixty-five cocaine-abusing methadone maintenance patients.', 'Participants received either standard methadone treatment or standard methadone treatment with CM for 3 months.', 'The HIV Risk Behavior Scale (HRBS) was administered prior to randomization to a study condition and 3 months after the study treatments ended. The primary objective indicator of drug use was longest duration of cocaine and opioid abstinence achieved during treatment.', 'Relative to those assigned to standard care, participants receiving CM significantly decreased overall HIV risk behaviors and injection drug use risk behaviors. CM participants also achieved longer durations of consecutive cocaine and opioid abstinence during treatment. Duration of abstinence achieved mediated the relationship between treatment condition and HRBS difference scores.'] Does contingency management reduce drug-related human immunodeficiency virus risk behaviors in cocaine-abusing methadone patients?