A 23-year-old woman became pregnant in the setting of long-standing severe pulmonary alveolar proteinosis. A previous twin gestation had resulted in low birth-weight infants. Progressive clinical and respiratory deterioration occurred, associated with exertional arterial oxygen desaturation. Because of the severity of her physiologic derangements and concern for the fetus, whole-lung bronchopulmonary lavage was performed twice under controlled conditions. This resulted in subjective and objective improvement, followed by successful term delivery.