This study estimates the impact of clinical and socioeconomic characteristics on health care use for HIV-infected patients. Data come from the Department of Veterans Affairs (VA) HIV Registry, which electronically extracts data from patients' automated medical records, and from patient interviews. Unlike prior studies, this analysis includes a staging system incorporating CD4 count and AIDS-defining diagnoses. Results showed that clinical factors were the most important determinants of health care use; socioeconomic variables were seldom significant. These findings were expected, since the VA is an equal access system, providing care regardless of socioeconomic status.