For diagnosing pulmonary disease on 82 occasions in 68 patients (64 males) aged 39 (23-73) years infected with HIV-1 we used flexible fiberoptic bronchoscopy (FFB) with bronchoalveolar lavage (BAL) or washing with or without transbronchial lung biopsy (TBB) and brushing. A clinical diagnosis of lower respiratory tract disease was obtained in 68/82 episodes (83%). An etiological diagnosis was reached by FFB in 59/82 episodes (72%). Pneumocystis carinii (PC), the dominating pathogen causing pneumonia in 54/82 episodes (66%), was detected by FFB in 51/54 (94%). In spite of being isolated in bronchoscopy material in 36/82 episodes (44%) cytomegalovirus (CMV) seemed to be the cause of pneumonia only in 2/36 (5%) episodes. Except PC and CMV, only bacteria (including mycobacteria) were found as infectious etiological agents. Kaposi's sarcoma and pulmonary edema were diagnosed in one patient each. For detection of PC in 37 episodes we compared staining of BAL fluid with indirect immunofluorescence (IF) using monoclonal antibodies (MoAB) with staining of BAL material by silver methenamine (Grocott). Staining with IF MoAB alone of BAL fluid only seemed to be even more sensitive than silver methenamine staining of BAL, TBB and brushing material. When using IF MoAB staining of BAL fluid, TBB and brushing added nothing to the result, except in the patient with Kaposi's sarcoma, diagnosed by TBB. Sputum investigation using IF MoAB for detection was increasingly adopted during the study time. It was very useful (sensitivity approximately 74%) and reduced the number of required FFBs.