OBJECTIVE To describe the clinical characteristics of 9 cases of idiopathic pulmonary alveolar proteinosis (iPAP) with secondary infections. METHOD The clinical and radiological data of 9 patients with iPAP and secondary infections admitted into Peking Union Medical College Hospital from 1st January 1990 to 1st January 2010 were retrospectively analyzed. RESULTS In that period, there were 97 patients of iPAP were admitted in our hospital. There were 9 patients of iPAP with secondary infections, aged (46.4 ± 14.6) y. There were 5 males and 4 females. Among them, 6 patients were misdiagnosed as interstitial pneumonia and corticosteroids were given to them. When the infection appeared, corticosteroids were still given to 3 patients, and the other 3 patients had stopped corticosteroids for 3 to 15 and a half months. Five patients had accepted mono-lung or whole lung lavage before 1, 2, 9, 14, 24 months. The clinical manifestations were fever (8 cases), cough (9 cases), expectoration (8 cases), hemoptysis (2 cases), chest pain (1 case) and moist rales (1 case). Glass-ground opacities (9 cases) and cavitations (4 case) were the main manifestations of chest radiology. Pleural effusions (1 case) was not common. The locations of infection was limited in chest: 9 cases had pulmonary infection and one case was associated with pleurisy. The infectious pathogens were the acid-fast tubercle bacillus (4 cases), fungus (3 cases, candida albicans, penicillium and aspergillus fumigatus for each one) and nocardia (2 cases, one case was associated with cytomegalovirus infection). FOLLOW-UP 6 patients were cured, 1 patient was improved and 2 patients were died. CONCLUSIONS For patients with iPAP, especially when they had been receiving corticosteroids, if they had fever and/or recently exaggerated dyspnea, especially whose chest radiology showed nodules and cavitations, the clinicians should be aware of infections diseases for them. Further specific microbiological studies and sufficient therapy should be obtained as quickly as possible.