This is believed to be the first reported case of disseminated mycotic infection complicating pulmonary alveolar proteinosis. The patient was hospitalized because of shortness of breath of two years' duration. He had suffered several episodes of malaise of respiratory origin. Histoplasmin and tuberculin tests were negative; sputum culture and gastric washings were negative for tuberculosis. Chest x-rays showed diffuse infiltration of tiny, poorly defined nodules throughout both lung fields. Microscopic study of lung biopsy revealed alveolar proteinosis. He was hospitalized three months later with hemoptysis, fever, cough, and profuse sweating. In spite of repeated therapy with antibiotics, intermittent fever continued. During the third week, surgical exploration drained an abscess in the left flank of pus containing Nocardia asteroides. A previously inoculated sputum culture also grew Nocardia. Treatment of the Nocardia infection resulted in improvement of all symptoms; however, the diffuse pulmonary lesions remained.