Three patients with the acquired immune deficiency syndrome (AIDS) or AIDS-related complex and lymphocytic interstitial pneumonia are reported. All patients presented with progressive dyspnea, nonproductive cough, fever, anorexia, weight loss, and arterial hypoxemia. Chest roentgenograms exhibited bilateral diffuse reticular-nodular densities. The diagnosis of lymphocytic interstitial pneumonia was made by fiberoptic bronchoscopy or open lung biopsy. Two patients were treated with corticosteroids, with significant improvement. The third patient died of pneumonia due to Pneumocystis carinii six months after the diagnosis of lymphocytic interstitial pneumonia was established. Serum antibodies to human immunodeficiency virus (HIV) were demonstrable in the two patients in whom the test was performed. Lymphocytic interstitial pneumonia is probably another pulmonary manifestation of AIDS or AIDS-related complex. Although the clinical presentation may be identical to the more common opportunistic infections, the treatment differs, and the prognosis may be better.