The authors describe a method to process induced sputum specimens for detection of Pneumocystis carinii which is simple, rapid and inexpensive. Induced sputum and bronchoalveolar lavage (BAL) were obtained within a 24-hour period from 41 patients who were HIV-positive and had pulmonary symptoms suspicious for P carinii pneumonia. Induced sputum or BAL fluid was placed into Saccomanno's fixative, blended, and centrifuged. The sediment was stained for P carinii cysts by a modified method with Fungi-Fluor Solution A (Polysciences, Warington, PA) and the Genetic Systems Pneumocystis carinii Immunofluorescence Antibody (Genetic Systems, Seattle, WA). The Genetic Systems stain on the BAL specimen was positive in 35 patients and was the standard for comparison. With a single induced sputum, the Genetic Systems stain detected 31 (89%) positive patients, whereas the Fungi-Fluor stain detected 21 (60%). The sensitivity for detecting P carinii cysts in induced sputum was significantly greater (P < 0.05) for the Genetic Systems stain.