Methadone maintenance is associated with improved adherence to antiretroviral therapies among HIV-positive illicit drug users; however, little information exists on whether adherence is associated with different drug abuse treatment modalities. Using longitudinal data from the Women's Interagency HIV Study, we evaluated the relationship between drug abuse treatment modality and adherence to antiretroviral therapies. In prospective analyses, individuals who reported accessing any drug abuse treatment program were more likely to report adherence to antiretroviral regimens > or = 95% of the time (AOR = 1.39, 95% CI = 1.01-1.92). Involvement in either a medication-based or medication-free program was similarly associated with improved adherence. Drug abuse treatment programs, irrespective of modality, are associated with improved adherence to antiretroviral therapies among drug users. Concerted efforts to enroll individuals with drug use histories in treatment programs are warranted to improve HIV disease outcomes.