Osteonecrosis has been found in association with non-traumatic pathological conditions such as alcoholism, sickle cell hemoglobinopathies, Gaucher's disease and decompression sickness. It is also a major compcation in surviving renal transplantation patients where it is generally believed to be a result of immunosupressive systemic corticosteroid administration. The precise etiology of osteonecrosis is still unknown, but many hypotheses have presented; interruption of the blood supply, direct cytotoxic effect, incresed intraosseous pressure and decreased venous return. Whatever the caused or the starting point, and whatever the pathologic process, blockage of the osseous microcirculation with intramedullary stasis appears to be the common denominator. In the present study, our purpose is to examine the microvascular structural changes and corresponding pathological changes of rabbit's femoral head by disturbance of lipid metabolism resulting from the administration of a large dose of the steroid. The results were as follows:1. In the study group (steroid-treated);there was a relatively increased empty lacuna within the rabbit's femoral head suchondral bone at 3 weeks in contrast with the control group. (control:10.72%, study:20.8%,P<0.01.). 2. Early definite marrow necrosis was found since 3 wekks, a marrow focal osteonecrosis since 5 weeks, and roentgenographically osteoporosis since 5 weeks in the study group. 3. In the histological study, the more degenerative vascular changes were found in the subchondral plate as weekly time was relapsed (H & E), and the subchondral vessels were filled with fat in most of the steroid-treated group (Oil-red 0). 4. In the microangiographic study, the chnges of vascular pattern of the subchondral area was found in the more steroid treated group. ie, it was shown to be dissimilar in size, irregulary spaced and not orderly arranged side by side in a line with disappearing focal vascular shadow.