Authors have studied 38 specimens of normal ligamentum teres(normal control group) and 78 specimens of the ligamentum teres in the femoral heads diagnosed as the avascular necrosis (avascular necrosis group). The relationships between histological changes of the ligmentum teres artery and degrees of avascular mecrosis of the femoral head were analyed. In normal control group, the luminal obliteration and wall hypertrophy of the ligamentum teres artery were visible only in 5% and 24% of cases, respectively. In avascular necrosis group, the luminal obliteration of the ligamentum teres artery were found in 46% of cases and the wall hypertrophy of the ligamentum teres artery were found in 53% of cases. In avascular necrosis group, there were no definite relationships between histological changes of the ligamentum teres artery and etiological factors or extent of the necrosis in the femoral heads. But more severe histological changes were found in advanced stages of the avascular necrosis. In cases of necrosis in fovea capitis area, changes of the ligamentum teres artery were more severe. From the above findings, authors conclude that the obliteration and hypertrophy in the ligamentum tere artery were followed in avascular necrosis of the femoral head, and these changes were influencing to the necrosis of fovea capitis region. But such chagnes of the ligamentum teres artery were not considered as primary causative factor of avascular necrosis of the femoral head.