Among 150 cases of microscopically proved Pneumocystis carinii pneumonia secondary to the acquired immunodeficiency syndrome (AIDS) seen by our pulmonary service from January 1982 to January 1986, P. carinii presented roentgenographically as a solitary pulmonary nodule in 2 patients (1.3%). It was the sole cause of the nodules as determined by clinical and roentgenographic response to specific drug therapy, examination of specimens obtained at fiberoptic bronchoscopy, and examination of lung specimens obtained at autopsy. In one of the patients, the nodule appeared to develop a large central cavity, which was confirmed at autopsy. In patients with AIDS, a solitary pulmonary nodule with or without cavitation may rarely represent P. carinii pneumonia.