A 56-year-old female with macrothrombocytopenia was scheduled for colectomy and hepatectomy. She had not shown significant bleeding tendency. Her preoperative platelet counts were 0.5-1.6 x 10(4) microliters-1 with the use of an automated cell counter. However, microscopic examination showed platelet number ranging 0.9-3.4 x 10(4) microliters-1 and many macrothrombocytes. Therefore, platelet biomass (platelet number x platelet volume) seemed almost normal. Bleeding time was 3 minutes and platelet function was normal. She received preoperatively high dose gamma-globulin administration and intraoperatively platelet transfusion. The operation was performed under combined epidural and general anesthesia. Intra- and post-operative course was uneventful.