We analyzed prospectively collected data from 211 HIV-infected patients who underwent bronchoscopy because of pulmonary symptoms during the period 1989-1991. We found an improvement in survival for patients diagnosed with Pneumocystis carinii pneumonia (PCP) in 1991 as compared to 1989 and 1990 (log rank test: p = 0.07). A significant decline in PO2 and CD4 cell count was observed in patients with PCP in the same period (p < 0.05 and 0.005 respectively). We suggest that the decline in CD4 cell count and in PO2 may reflect a change in Pneumocystis carinii transmission, and that the improved survival may be a result of altered treatment strategy of PCP.