Pulmonary involvement is a serious complication in Gaucher disease, as is neuronopathic involvement. Few reports are available, however, on the frequency, clinical course and therapy for pulmonary involvement in patients with Gaucher disease. We report a case of type 2 Gaucher disease with severe hepatosplenomegaly, anemia, hypertonia, and psychomotor retardation. The diagnosis of Gaucher disease was confirmed by the presence of Gaucher cells in bone marrow and low serum beta-glucocerebrosidase activity (patient, 0.8; control, 4.1-9.7 nmol/mg.protein/hr) at the age of 1 year. The patient's genotype is L444P/unknown. Enzyme replacement therapy (ERT) with intravenous imiglucerase at 78 U/kg/2weeks was started, and hepatosplenomegaly and laboratory abnormalities were markedly improved after 6 months of therapy. After 8 months of therapy, respiratory impairment appeared together with a decrease of tidal volume and low SpO2 during sleep. Serum acid phosphatase and angiotensin converting enzyme levels mildly increased, and radiological findings showed bilateral ground-glass appearance without signs of respiratory infection. With the diagnosis of progressive pulmonary involvement in Gaucher disease, we increased the dosage of imiglucerase from 50 to 75 U/kg/2 weeks. After a month, respiratory symptoms and CT findings of ground-glass appearance remarkably improved, but interlobular septal and intralobular interstitial thickening persisted. The maximum permitted dosage of imiglucerase in Japan is 60 U/kg/2 weeks. Based on our experience with this case, we propose that a higher ERT dosage would be uselul for serious pulmonary involvement.