Since the advent of highly active antiretroviral therapy (HAART), the incidence of opportunistic infections (OI) in patients with HIV has markedly decreased. Despite this, there are still large numbers of Pneumocystis carinii pneumonia (PCP) cases at Cook County Hospital (CCH). To better understand this patient group, we performed a retrospective chart review of 120 pathologically proven cases of PCP from January 1998 to June 2001. One hundred four patients were included in the study. Sixty-nine percent of our patients were active substance abusers and 50% had previous knowledge of HIV disease. Of our patients, fewer than 5% were on HAART or PCP prophylaxis on study admission. The overall mortality rate was 14%. Of discharged patients, 65% were placed on HAART therapy and 59% of these achieved a viral load of less than 1000 copies per milliliter in the year postdischarge. Patients who failed to achieve a viral load less than 1000 copies per milliliter were more likely active substance abusers or had a viral load greater than 100,000 copies per milliliter prior to study admission. Our study shows that patients are still being admitted with PCP in the HAART era. Active substance abuse and failure to recognize HIV status contributed heavily to this late presentation of HIV disease. An aggressive approach toward HIV identification and substance abuse treatment may decrease admissions to the hospital for PCP and improve response to HAART therapy.