The Ryan White CARE Act supports comprehensive care to persons with HIV infection. With an annual budget of over $1 billion, it is the largest federally funded programme for HIV care in the USA. We analysed data from the HIV Costs and Services Utilization Study, a nationally representative sample of HIV patients. Patient data were collected in 1996-97 and clinic data were collected in 1998-99. We examined whether CARE Act funded clinics differed from other HIV clinics in (1) the characteristics of their patients, and (2) their organization, staffing, and services. We found that patients at CARE Act clinics were younger, less educated, poorer, and more likely to be female, non-white, unemployed, uninsured, and have heterosexual contact as an HIV risk factor, compared to patients at other HIV clinics. CARE Act clinics tended to specialize in HIV care, had more infectious disease specialists, had fewer total patients, and provided more support services (e.g. mental health, nutrition, case management, child care). These results are consistent with findings of other studies that were limited by non-probability samples or restricted geographical areas.