We evaluated the sensitivity of bronchoscopy for the diagnosis of Pneumocystis carinii and cytomegalovirus pulmonary infections in patients with acquired immunodeficiency syndrome. The antemortem and postmortem diagnoses were compared in 36 patients who underwent fiberoptic bronchoscopy within two weeks of death. In autopsy-proved cases of Pneumocystis carinii pneumonia (PCP), the organism was correctly identified antemortem in 22 (88%) of 25 cases, including 94% of adequate transbronchial bronchoscopic biopsy specimens, 95% and 88% of bronchoalveolar lavage (BAL) cell blocks and smears, respectively, and 79% of brushing. In 11 patients who underwent simultaneous adequate biopsy, BAL, and brushings, the diagnostic sensitivity for PCP was 100%. The negative predictive value of bronchoscopy for PCP was 85%. Bronchoscopy yielded the diagnosis of cytomegalovirus infection in only 55% of autopsy-proved cases. Diagnostic sensitivity was also reduced when an important diagnostic procedure, such as transbronchial biopsy or BAL, was inadequate or not performed.