Bronchoalveolar lavage (BAL) was performed in 51 adult immunocompromised patients (30 acquired immunodeficiency syndrome [AIDS] and 21 non-AIDS) as part of an extensive diagnostic evaluation for diffuse pulmonary infiltrates. Because multiple episodes occurred in several patients, a total of 60 BALs were performed. A diagnosis of fungal pneumonia was eventually made in 12 patients (24 percent). The organism was identified in BALs from seven of the 12, including five of seven cases of cocciodoidomycosis, one of two cases of aspergillosis, and one of three cases of cryptococcosis. Among the AIDS patients, only one case of coccidioidomycosis was diagnosed, whereas six such diagnoses were made from the 25 BALs performed on the 21 non-AIDS patients. This suggests that coccidioidomycosis is not as frequent an infection in AIDS patients in this endemic area as has been suggested previously. Candida-like organisms were identified in 23 BALs, but in no case were they clinically pathogenic. Their presence correlated with oral candidiasis (p = 0.01). Twenty-seven of 29 episodes related to Pneumocystis carinii were identified by Papanicolaou-stained cytocentrifuged BAL preparations, all but two of which were in AIDS patients. In addition, BALs detected six episodes of bacterial pneumonia and three of five cases of radiation pneumonitis. Overall, the diagnostic sensitivity of BAL was 52 of 60 or 87 percent. While examination of induced sputum for the presence of Pneumocystis may eliminate the need for bronchoscopy in some AIDS patients, BAL remains an excellent diagnostic procedure in the immunocompromised patient without AIDS.