Flexible fiberoptic bronchoscopy with bronchoalveolar lavage was performed in 16 pediatric patients with the acquired immunodeficiency syndrome (AIDS) and deterioration in pulmonary function suggestive of opportunistic infection. In 62% of the patients Pneumocystis carinii was identified. Culture results showed a pure growth of Pseudomonas aeruginosa for one patient in addition to the Pneumocystis carinii. Bronchoscopy with lavage was well tolerated, with few complications even among patients with significant tachypnea and hypoxia. Because of its relative safety and effectiveness, this procedure should be considered the first invasive measurement used for evaluation of parenchymal lung disease in this population of patients.