To determine adherence by health care providers to guidelines for antiretroviral therapy and for prevention of opportunistic infections (OIs) in adults with HIV infection in federally funded facilities in the United States, we reviewed records of HIV-infected adults (>13 years) in 11 Ryan White Title III facilities in four states for information on eight standard-of-care recommendations during November 1996 through September 1997. Eligibility required a visit to the facility within 6 months before record abstraction and a lowest CD4+ lymphocyte count <500 cells/microl. Reviews were completed for 148 patients in Maryland, 355 in New York, 370 in Georgia, and 538 in Illinois. Adherence to prevention measures by health care providers was >85% for HIV plasma RNA testing, prescription of antiretroviral therapy, Pneumocystis carinii pneumonia (PCP) prophylaxis, anti-Toxoplasma antibody testing, and obtaining Papanicolaou (Pap) smears but lower (69%-80%) for Mycobacterium avium complex (MAC) prophylaxis, tuberculin skin testing (TST), and pneumococcal vaccination. Adherence was similar by patient age, gender, racial/ethnic group, urban versus rural, and hospital versus clinic setting but was generally lower for injecting drug users (IDUs) than for patients with other HIV exposures (p < .05 by multivariate analysis for TST, anti-Toxoplasma antibody testing, Pap smear, and measurement of HIV plasma RNA). Adherence by health care providers to guidelines for preventing OIs in these federally funded facilities is generally high but could be improved for some prevention measures, for instance, MAC prophylaxis, TST, and pneumococcal vaccination, especially for IDUs.