Testing and counseling, along with community outreach, have been identified as valuable in the prevention of human immunodeficiency virus (HIV) and other blood-borne diseases. This article assesses the extent to which outpatient substance abuse treatment (OSAT) programs provide such services. Longitudinal data for 1988-2000 were analyzed from the National Drug Abuse Treatment System Survey (NDATSS). Random-effects regression was used to examine factors associated with the provision of prevention services. HIV testing, which had became more common between 1990 and 1995, continued to proliferate between 1995 and 2000. The proportion of units that provide HIV testing and counseling increased from 66% to 86%. The proportion of units that provide HIV community outreach increased significantly before 1995 but then slightly decreased from 77% to 73% between 1995 and 2000. In conclusion, HIV testing and counseling widely proliferated in OSAT care. However, OSAT units remain less likely to offer HIV community outreach services.