A 44-year-old woman with pulmonary alveolar proteinosis was treated by repeated unilateral bronchopulmonary lavages over 6.5 years. The effectiveness of the treatment was assessed by Xe-133 scintigraphy as well as lung function tests and chest roentgenograms. Xe-133 scintigraphy clearly demonstrated improvement of regional ventilation and perfusion, and equalization of the ventilation and perfusion ratio. Therefore, Xe-133 scintigraphy was found to be useful in the analysis of changes in regional aeration, ventilation, and perfusion before and after bronchopulmonary lavage in pulmonary alveolar proteinosis.