A fall in systemic arterial pressure after implantation of acrylic cement into the acetabulum and proximal femoral shaft in the surgery of total hip prosthesis was observed and also the following results were obtained in three cases of total hip prosthesis under general anesthesia. 1) Blood pressure was usually decreased immediately after implantation of acrylic cement and returned to normal level approximately within 5 minutes. 2) The marked fall in blood pressure was more often observed with the introduction of bone cement into the proximal femoral shaft but less with the acetabular implantation of bone cement. 3) It is urged to measure blood pressureat the minute interval immediately after insertion of bone cement.