In the first part of the study we examined the accuracy of femoral anteversion (AV) determined by fluoroscopy, simulating a method used in closed intramedullary femoral nailing. Twenty cadaveric femora were used. The condyles and posterior trochanteric area were resting on a horizontal table. The proximal femur was imaged using a C-arm image intensifier with horizontal X-ray beam at an angle of 30, 45, or 60 degrees to the long axis of the femoral shaft. To evaluate the reliability of the measurements, the real AV angle was determined by radiography. A small difference (mean 2 degrees ) was found between the real AV angle and the angle between the horizontal plane and the central head-neck axis (NH angle) as displayed by the image intensifier. In a separate clinical study, the NH angle was assessed and used as a guide to intraoperative rotational reduction in ten patients with femoral shaft fracture using the aforementioned method. Follow-up examinations of the AV angle showed that rotational deformities of clinical significance were avoided.