Bone marrow pressure is neither arterial pressure nor venous pressure of extremity, that is thought the precapillary pressure of bone. It is different between long bone and flat bone, and is also different in various site of the bone. Author measured bone marrow pressure of 84 normal femoral heads of Korean adults for basic data of early diagnosis of avascular necrosis of femoral head. The results are followings : 1. The baseline bone marrow pressure of Korean healthy adults is average 22.5 ±7.2mmHg. 2. The most significant change of bone marrow pressure in stress test is observed at 5 min. after injection of 5cc normal saline. 3. The increase of bone marrow pressure at 5 min. after stress test was average 7.4 ±4.4 mmHg. 4. Sex and age factors do not influence bone marrow pressure.