A retrospective review of the charts of patients with the acquired immunodeficiency syndrome (AIDS) was performed at three university-affiliated teaching hospitals in Denver between May 1982 and April 1987. Patients were evaluated for the presence or absence of Pneumocystis carinii pneumonia (PCP) and for the occurrence of pneumothorax at any time during their clinical course. The incidence of pneumothorax in AIDS patients with PCP was 9.0 percent (8/89), compared with 0 percent (0/45) in AIDS patients without PCP (p less than 0.03). All of the pneumothoraces resolved, most without chest tube placement. This study suggests that in patients with AIDS, PCP is associated with an increased incidence of pneumothorax, while AIDS patients without PCP are not at increased risk for the development of pneumothorax.