A 3-year-old HIV-positive boy developed Pneumocystis carinii pneumonia (PCP) resulting in chronic interstitial pulmonary disease, which persisted for the following 3 years; he was essentially asymptomatic and the lung findings had therefore been attributed to lymphocytic interstitial pneumonia (LIP). He subsequently developed extensive cystic pulmonary disease, documented by CT, leading to recurrent pneumothorax and severe pulmonary insufficiency. Lung biopsy revealed chronic PCP infection associated with extensive pulmonary fibrosis and calcification. This case suggests that Pneumocystis carinii may cause chronic progressive pulmonary fibrosis with cyst formation and respiratory failure.