Atelocollagen have been used recently in skin and other soft tissue defect regions more than silicone fluid because of the low incidence of an immune reaction and complications. Several cases of acute pneumonitis after a subcutaneous injection of silicone have been reported. The symptoms were dyspnea, fever, chest pain and hemoptysis. Previous reports have explained the pathophysiology of acute pneumonitis to a pulmonary microembolism and cellular inflammation. We experienced two cases of an acute interstitial pneumonitis and pulmonary hemorrhage after a subcutaneous injection of atelocollagen. They were all healthy young women and complained of dyspnea, fever and blood tinged sputum. The chest radiography and computerized tomography showed a bilateral ground glass opacity in both lung fields. One case recovered completely with conservative treatment but the clinical course of the other case was aggravated to the degree that invasive positive pressure ventilation therapy was required. We report a rare case of a diffuse pulmonary alveolar hemorrhage and an interstitial pneumonitis after the subcutaneous injection of atelocollagen for cosmetic purposes.