Avascular necrosis of the femoral head is the most common disease for which total hip arthroplasty is being performed in Korea. In order to develop a femoral stem having a proper fit to Korean femur, it is essential to study the change in the shape of the proximal endosteal canal of the femur resulting from disuse caused by pain avascular necrosis of the femoral head. The size and shape of the proximal femur were measured with 3-dimensional images reconstructed from the CT data of 116 femurs in 58 patients who had suffered from avascular necrosis of the femoral head. Among them, there were 30 patients who had suffered from unilateral involvement of avascular necrosis of the femoral head. The comparative study was made on the shape of the proximal endosteal canal of the femur between the normal and the diseased femurs. The shape of proximal endosteal canal of femur in avascular necrosis didn't show statistically significant difference from that of the normal femur. Therefore, the femoral stem designed from the data of normal femurs can be usually applied to the avascular necrosis without problem in obtaining the maximal fit between the stem and the endosteal canal. The canal flare index was greater and the proportion of champagne-flute type was higher in Korean than in Westerner. The shape of the endosteal canal of isthmus was nearly circular in Korean in contrast to anteroposteriorly ovoid in Westerner. The distribution of sagittal canal flare index which was newly defined in this study was entirely different from that of preexisting canal flare index in coronal plane. It will be necessary to study further in the future.