Pulmonary alveolar proteinosis is a rare disorder in which lipoproteinaceous material accumulates within the alveoli. We report a case of pulmonary alveolar proteinosis in a 41 year old female patient. She complained of a dry cough in the preceding 6 months. She presented symptoms of mild hypoxemia and diffuse infiltration at both lower lung fields. A milky fluid was obtained by bronchoalveolar lavage. We confirmed by light microscopic examinations of the lung tissues obtained by transbronchial lung biopsy. Through several follow-ups, the patients symptoms were mild.