Patients with acquired immune deficiency syndrome (AIDS) are at increased risk for pneumothorax, which usually occurs in the setting of Pneumocystis carinii pneumonia. The rationale of the present study was based on the hypothesis that the increased incidence of pulmonary tuberculosis in human immunodeficiency virus (HIV)-infected patients could favour the development of pneumothorax in such patients. A case-control study was performed comprising 140 HIV-infected patients grouped as follows: 35 patients with pneumothorax and 105 matched controls without pneumothorax. Univariate analysis identified four risk factors for pneumothorax: 1) previous P. carinii pneumonia (p=0.01); 2) current P. carinii pneumonia (p=0.02); 3) pulmonary tuberculosis (p=0.01); and 4) cysts, pneumatoceles or bullae on chest radiographs (p<0.001). Multivariate analysis indicated that current P. carinii pneumonia (p=0.01) and pulmonary tuberculosis (p=0.04) were both independent risk factors for pneumothorax. In conclusion, our findings demonstrate that, in addition to Pneumocystis carinii pneumonia, pulmonary tuberculosis enhances the risk of pneumothorax in patients with acquired immune deficiency syndrome.