Fibreoptic bronchoscopy is an established diagnostic procedure for HIV-associated pulmonary infections. We retrospectively evaluated the diagnostic effectivity and safety of fibreoptic bronchoscopy with bronchoalveolar lavage (BAL) and transbronchial biopsy (TBB) in 153 patients with late-stage HIV infection and clinical signs of pulmonary infection or abnormal chest radiograph. Bronchoscopy leads to diagnosis in 82.4% and changed therapy in 54%. 45 patients (30%) were found to have pneumocystis carinii pneumonia (PCP), the most common bronchoscopic finding, followed by bacterial lung disease (29.3%). BAL had a sensitivity of 78% for PCP. Diagnostic yield of BAL for PCP was higher in patients without previous treatment (positive results in 82%) with regard to PCP independend of the prior treatment. Serious complication occurred in 22 cases (pneumothorax: 6 (3.9%), bleeding: 12 (7.8%), hypoxaemia: 4 (2.6%)). High serum levels of lactate dehydrogenase (LDH) correlated with pulmonary complications like pneumothorax. Age, sex and kind of pulmonary infection did not influence complication rates. 6 (3.9%) episodes of spontaneous pneumothorax occurred in the further course, 3 of them concurrently with PCP or prior history of PCP. We conclude that fibreoptic bronchoscopy is of great value for diagnosing pulmonary infection in HIV-seropositive patients. TBB provides incremental diagnostic information not available from BAL, especially in patients pretreated with cotrimoxazol or pentamidin. For that reason we believe that TBB should be performed in these patients.