Kaposi's sarcoma (KS) is the most common neoplasm in persons infected with the human immunodeficiency virus (HIV). However, information about the presenting features of pulmonary KS is limited. To describe the clinical, laboratory, and radiographic features of pulmonary KS, medical records and chest radiographs of 168 patients with pulmonary KS diagnosed by bronchoscopy during a 7-yr period were reviewed. All of the patients were HIV-seropositive males, of whom 95% identified homosexual or bisexual sex as a risk factor for HIV infection. The median CD4 lymphocyte count was 19 cells/microliter. The most common symptoms were cough, dyspnea, and fever. Patients with a concurrent opportunistic pneumonia had a higher median serum lactate dehydrogenase (LDH) concentration than did those with pulmonary KS alone (p<0.001). The most common chest radiograph findings were bronchial-wall thickening, nodules, Kerley B lines, and pleural effusions. The presence of granular opacities or cystic spaces usually indicated concomitant Pneumocystitis carinii pneumonia (p < 0.001). Twenty-six patients (15.5%, 95% CI = 10.2% to 20.8%) had pulmonary KS in the absence of mucocutaneous involvement. The presentation of pulmonary KS is characterized by symptoms that cannot be distinguished from those of a superimposed infection. An elevated serum LDH concentration or a chest radiograph with granular opacities or cystic spaces should raise the suspicion of concurrent opportunistic pneumonia. The diagnosis of pulmonary KS should be considered in an HIV-infected homosexual or bisexual male with respiratory symptoms even in the absence of mucocutaneous lesions.