Individuals with serious mental illness are at higher risk for HIV than are members of the general population. Although studies have shown that individuals with serious mental illness experience less adequate care and worse physical health outcomes than comparable patients without serious mental illness, little is known about HIV care among individuals with serious mental illness who become infected with HIV. In the present study, we describe patterns of highly active antiretroviral treatment (HAART) use and physician monitoring received by 154 patients with serious mental illness infected with HIV. Participants were recruited from mental health agencies in Los Angeles, California. Data from 762 HIV-only patients from a separate Western U.S. probability sample were used for comparison. High proportions of serious mental illness patients with HIV in our sample appeared to be receiving adequate HIV care. Fifty-one percent of all serious mental illness patients with serious mental illness with HIV were taking HAART, and the majority received close monitoring of their CD4 counts (84%) and viral loads (82%) throughout a 1-year period. HAART use and patterns of CD4 count and viral load monitoring did not differ significantly between patients with both serious mental illness and HIV, and patients with HIV only (all p > 0.05). Specialized programs providing assistance to serious mental illness populations with HIV may be helping to narrow health care disparities as a result of having serious mental illness.