Forty femoral neck fractures were followed for 5 years in a prospective clinical, roentgenographic and scintimetric investigation. Thirteen cases had uncomplicated healing, 22 necrosis and five non-union. The diagnostic value of radiographic changes was analysed with reference to development of necrosis of the femoral head or non-union. Sclerosis of the femoral head, and compression and displacement of the fracture were compatible with eventual healing and clinical recovery. Subchondral fracture and collapse of the load-bearing surface, diagnostic for necrosis, were observed in only 7 of 22 cases at 1 year and as late as 3-5 years in three cases. By contrast, four out of five non-union cases were established radiographically within 1 year. Patients needing an arthroplasty after fracture of the femoral neck should be identified on clinical grounds after early radionuclide scintimetry. Waiting for radiographic documentation of necrosis in cases with pain will increase the risk for physical and social impairment associated with poor function of the hip.