We report a 39-year-old male with pulmonary alveolar proteinosis. Although no abnormal shadows were seen on regular check-up chest roentgenogram one year previously, diffuse alveolar filling shadows were noted on admission, suggesting fairly acute progression of the disease. He was treated with bronchoalveolar lavage of each segment of both lungs by flexible fiberoptic bronchoscope under local anesthesia. Following this treatment, the shadows on X-ray film and shortness of breath resolved. Oxygen tension of arterial blood, pulmonary function, and serum CEA recovered to almost within normal ranges. The shadows deteriorated twice, but therapeutic lavage performed at the outpatient clinic was effective on each occasion. He thus received 3 series of bronchoalveolar lavage over a period of more than 3 years. We followed the clinical course of this patient for 6 years, and he remained well 3 years after the final treatment.