Five cases of Pneumocystis carinii infection with evidence of lung tissue destruction that occurred in patients with the acquired immunodeficiency syndrome were reviewed. None of the patients had a history of cigarette smoking, but all five had either cavitarylike lesions in the lungs or had pneumothorax at the time of presentation to the hospital. All patients had P carinii identified in specimens obtained either from bronchial washings or from open-lung biopsy. In four of the five patients, no other pathogens were involved in the lungs, while the fifth patient had concomitant cytomegalovirus infection. Findings on chest roentgenograms included large thin-walled cavitarylike lesions, multiple cavitary lesions, or pneumothorax. These presentations of the infection have not been previously described, and the mechanisms for lung tissue damage are as yet unknown. Cavitary lung disease found on chest roentgenograms in patients should not exclude the diagnosis of P carinii pneumonia, and patients with the acquired immunodeficiency syndrome presenting with pneumothorax should have the possibility of P carinii infection included in the differential diagnosis.