Most insufficiency fractures of the femur are transverse fractures of the femoral neck. We report two 77-year-old female patients with longitudinal fractures of the femoral shaft; one had a vertical fracture line in the proximal part of the shaft and the other a spiroid line in the middle third of the shaft. Both patients experienced apparently spontaneous onset of incapacitating mechanical pain in the hip or thigh; duration of the pain at evaluation was ten days in one case and six months in the other. Potential risk factors were osteoarthritis of the hip and the presence of metalwork in the knee. Increased radionuclide activity at the fracture site was seen on the bone scans. In one patient, roentgenographic and computed tomography findings were normal and the diagnosis was established by magnetic resonance imaging. In the other, the fracture line was seen clearly on computed tomography sections. Longitudinal fractures often escape diagnosis initially because roentgenographic changes are delayed. Hyperactivity on the bone scan is suggestive but sometimes so extensive as to mislead the diagnosis. The callus and, less frequently, the fracture line are sometimes seen on computed tomography sections. The role of magnetic resonance imaging remains to be determined.