After femur neck fracture, many techniques have been known for early detection of the viability of the femoral head which is very important to decide method of treatment. At the present time, bone scan with 99mTc-MDP is the best available radioistope for use in scanning, because it is very sensitive, non-invasive and simple, minimal radiation dose, easily reproducible. Bone scanning was carried out in 18 cases of femur neck fractures from July, 1981 to October, 1982 in Kyung Hee University Hospital. The results were as follows: l. In twelve cases in which radiological confirmation of viability of the femoral head was difficult to make, we could confirm the presence or absence of vascularity of femoral head using bone scan. 2. Six cases which were considered to have vascular impairment to the femoral head radiologically, were identified to have vascular impairment to the femoral head by bone scan and these were evidenced by operative findings and by histology of biopsy specimen. 3. In fresh fractures, we identified the vascular impairment by the bone scan minimally 5 days after injury. 4. In old fractures, we could confirm the viability of the femoral heads by bone scan. 5. Bone scan is considered to be the excellent technique for early detection of the vascular impairment to the femoral head after femur neck fractures.