A 33-year-old man was admitted to our hospital because of thrombocytopenia found on a periodic physical examination. Splenomegaly was recognized Peripheral blood showed WBC 4,510/microliters, Hb 12.5 g/dl, and Plt 40,000/microliters. Increased serum levels of acid phosphatase and angiotensin converting enzyme were observed on laboratory tests. Bone marrow aspirate revealed Gaucher cells. Decreased beta-glucosidase activity was demonstrated in blood leukocytes, cultured blood lymphocytes, and cultured bone marrow fubroblasts from the patient. His glucocerebrosidase genotype was T1448C/C1504T (L444P/R463C). Since neurological examination and skeletal X ray results were normal, Gaucher disease type 1 was diagnosed.