Cardiac tamponade following sternal puncture is fatal and is caused by an anomaly such as foramen sterni, fragility of the bone, or high pressure exerted by doctors on the bone. Contact pressure associated with bone marrow aspiration is unknown;therefore, we examined the contact pressure resulting from bone marrow puncture for aspiration. Prescale, a pressure-sensitive film, was used for measurements. Contact pressure on wood surface at 2 heights, the knee and hip positions of the hematologists, was examined and was approximately 15 - 21 megapascals. The magnitude of the con-tact pressure did not change with the type of puncture needle. However, the contact pressure in the needle area at the hip position was higher than that at the knee position height, when doctors aspirated the bone marrow. Contact pressure resulting from bone marrow puncture was found to be high;therefore, hematologists should be aware of this force when dealing with patients.