The reactive interface between live and dead bone at the periphery of AVN lesions had a characteristic MRI appearance that facilitated diagnosis. Based on central signal intensity on T1WI and T2WI, lesions could be seperated into four classes according to classification suggested by Mitchell that correlated with radiographic and clinical staging. Detection of premature conversion to fatty marrow has important implications regading the pathogensis of AVN and may aid early diagnosis. To explore the ability of magnetic resonance imaging (MRI) in diagnosis of avascular necrosis of the femoral head, MR images of 36 proved AVN lesions were compared with radiographic stagings(n=36), radionuclide imagings(n=26), clinical findings(n=36) and histologic examinations (n= 28) from September 1990 to July 1992. The following results were obtained: 1. Radiographic findings were normal in 1796 (6/36) of the lesions which were in MRI class A in 4 cases, B in 1 cases, C in 1 case. 2. Radionuclide scan showed normal in 1596 (4/26) of the lesions which were in MRI class A in 3 cases, B in 1 case. 3. Clinical symptoms were absent in 1496 (5/36) of the lesions which were MRI class A in 4 cases, B in 1 case. 4. Histologically were classified by Arlet and Durroux into four types. 24 cases were Type 3,4 which were MRI Class A in 2 cases, B in 1 case, C in 1 case, D in 20 cases. Conclusively, MRI should be the imaging modality of choice for early evaluation of exact location and extent of AVN than radiograph and radionuclide scan.