Bioptic and scintigraphic methods of diagnosing avascular necrosis of the femoral head following intracapsular fracture of the femoral neck were compared. During operative treatment of patients, biospy samples of bone marrow were taken from the femoral head about 2 hours after the intravenous injection of sup(99m)Tc-Sn-pyrophosphate; histological examination of the biopsies were also performed. Scintigrams of the femoral head using sup(99m)Tc-pyrophosphate were performed 2 days, 7 days and 6 weeks post-operatively. The biopsies confirmed no morphological changes being apparent in the first few days. The biopsy samples indicated two groups of patients with either high or low activity in the femoral head. However, it was concluded that the use of bone-seeking radionuclides with this technique might be more reliable. Scintigraphic trends divided the patients into three groups, one with persistently normal, another with varying, and a third with decreased activity in the femoral head. It was concluded that very early scintigraphy is probably not the method of choice since the images were often difficult to interpret. For the present, assessment of the viability of the femoral head should rest upon scintigraphic examinations performed about 6 weeks or 3 months after the injury.