Background: Recent reports have described osteonecrosis of the femoral head after intramedullary nailing of the femur through the piriformis fossa in children. Other reports have raised concerns about the development of femoral neck narrowing and valgus deformity of the proximal part of the femur after intramedullary nailing through the tip of the greater trochanter. We evaluated the radiographic changes in the proximal part of the femur following intramedullary nailing through the lateral trochanteric area at a minimum of two years postoperatively in twenty-five affected extremities. The mean age of the patients at the time of the index procedure was ten years and six months. Methods: A retrospective radiographic review was performed to look for proximal femoral changes. Specifically, the radiographs were examined for evidence of osteonecrosis. The articulotrochanteric distance, femoral neck diameter, and neck-shaft angle were measured on the initial and final radiographs. Results: No patient had evidence of osteonecrosis of the femoral head. The articulotrochanteric distance decreased by a mean of 0.4 mm, the femoral neck diameter increased by a mean of 4.9 mm, and the neck-shaft angle decreased by a mean of 1.4°. Compared with a group of seventeen patients with adequate initial and final radiographs of the contralateral side, the final mean articulotrochanteric distance was 4.5 mm less on the involved side than on the uninvolved side, the mean femoral neck diameter was 0.7 mm less on the involved side than on the uninvolved side, and the mean neck-shaft angle was 3.2° less on the involved side than on the uninvolved side. No patient had development of clinically important femoral neck narrowing or valgus deformity. Statistically, the likelihood that these data represent a group with a mean 3-mm increase in the articulotrochanteric distance is <1%. The likelihood that these data represent a group with a mean 3.2-mm decrease in the ultimate femoral neck diameter is <1%. The likelihood that these data represent a group with a mean 5° increase in the neck-shaft angle is <1%. Conclusions: Lateral transtrochanteric intramedullary nailing in children who are nine years of age or older does not produce clinically important femoral neck valgus deformity or narrowing, and we did not observe osteonecrosis of the femoral head after this procedure. Level of Evidence: Therapeutic study, Level IV (case series [no, or historical, control group]). See Instructions to Authors for a complete description of levels of evidence.