We evaluated longitudinal changes in chest CT images in six cases (5 males and one female, age: 35-57 yr) of pulmonary alveolar proteinosis treated with bronchopulmonary lavage. Chest CT images on admission showed a mixed pattern of air-space consolidation and reticular or reticulonodular shadows in most cases and showed a peripheral clear zone in all cases. These shadows gradually diminished after bronchopulmonary lavage. Some cases revealed early improvement in the hilar zone while others had equal improvement in all lung lesions. In one case, consolidation was changed into reticular shadows by treatment. Previous reports have indicated that "interstitial shadows which disappeared with lavage" reflect edematous thickening of interlobular septa. However, our longitudinal evaluation suggests that interstitial shadows on CT images may reflect not only real interstitial infiltration but also inhomogeneous distribution of intralobular deposits.