We report on two cases of alveolar hemorrhage after inhalation of detergent aerosol. Case 1: A 54-year-old woman was referred to our hospital with a complaint of hemoptysis. She used a spray type detergent for ventilation fan cleaning, and recognized hemoptysis later for eight hours. She had mild anemia and severe hypoxemia, and chest radiographs and CT films infiltrative shadows were recognized predominantly in the right middle, left lingual lower lobes. Case 2: A 22-year-old woman was admitted to our hospital complaining of bloody sputum and dyspnea. She had used a spray-type detergent for bathroom cleaning intermittently for one week. Between the beginning of this activity and the seventh day, cough and dyspnea developed. Chest radiographs and CT films disclosed diffuse infiltrative shadows in both lung fields. In both cases, the condition was diagnosed by bronchoalveolar lavage as alveolar hemorrhage. In case 2, a transbronchial lung biopsy specimen revealed alveolitis without vasculitis or capillaritis. Both the clinical symptoms and the CT images were improved by steroid administration. The steroid dosage was decreased gradually and stopped, but there was no relapse of the hemoptysis. Neither patient was positive for antinuclear antibodies or antibodies against the cytoplasm of granulocytes. Urinalysis showed no pathological findings. Since the hemoptysis appeared after inhalation of a detergent aerosol, it was possible that inhalation was the cause of the hemorrhage.