PURPOSE: To evaluate the clinical significance of the multiple increased uptake lesions other than in femoral heads as seen on whole body bone scan in patients with avascular necrosis of femoral heads. MATERIALS AND METHODS: One hundred and seventy three patients with clinical diagnosis of avascular necrosis of fthe emoral head underwent a bone scan using Tc-99m MDP. Increased uptake lesions other than in femoral heads were evaluated, including frequency and common sites of involvement, and correlated with clinical information and plain radiographic findings. Two hundred patients without AVN, who had undergone a bone scan, were included as a control group. RESULTS: Increased uptake lesions in extrafemoral head locations were found in 36 of 173 patients(20.8% ; the location of 79 lesions was other than the femoral head, This result is statistically different from patients without avascular necrosis of femoral head(p<0.0001). The most common site of involvement was the knee joint area(62.5%). Other lesions were located in the mid-shafts of the long bones of the lower extremities, calcaneus, proximal humerus, etc., in order of decreasing frequency. Plain radiographs of 17 lesions were nonspecific, except for three lesions showing definite changes associated with avascular necrosis. The risk factors included alcoholism, the prolonged use of steroids, renal transplantation, herbal medication and working as a working as deep-sea diver. Most patients did not complain of pain, except for two with irreversible osteonecrotic changes as seen on plain radiograph. CONCLUSION: in patients with avascular necrosis of the femur, increased uptake lesions other than in the femoral head as seen on bone scan, may represent the early stage of osteonecrosis, which shows a characteristic appearance on bone scan. In order to avoid possible misdiagnoses of multiple extrafemoral lesions as bony metastasis or traumatic lesions, in patients with avascular necrosis of the femur these should be carefully evaluated.