Pulmonary alveolar proteinosis(PAP) is thought to be a rare disease of unknown etiology characterized by the accumulation of strong PAS-positive lipoproteinaceous material in the pulmonary alveolar spaces. The defect in the clearance and degradation of intra-alveolar phospholipoproteinaceous material in PAP likely represents dysfunction of type II pneumocytes. Although the causative treatment of PAP is not well known, yet whole lung bronchopulmonary lavage is a relatively safe and effective treatment. We experienced three cases of PAP, which were confirmed by light and electron microscopic examinations of lung tissues obtained by open lung biopsy, transbronchial lung biopsy and lung lavage, so we present 3 cases of PAP with a review of the literature.