PURPOSE: To evaluate an efficacy of immediate closed reduction and hip spica casting in pediatric patients with femoral shaft fractures. MATERIALS AND METHODS: 27 cases of 27 pediatric patients who had been treated conservatively for the femoral shaft fractures under 10 years of age were retrospectively reviewed. The cases with serious associated injuries were excluded. The hospital stay, duration of traction and hip spica cast, frequencies of plain radiographs, clinical and radiological outcomes at the final follow-up, and financial aspects were evaluated comparatively between the groups of immediate hip spica casting(12 cases) and traction-casting(15 cases). RESULTS: The patients treated with immediate hip spica casting had a mean hospital stay of 7.8 days, compared with a mean of 25.8 days for those treated with traction and casting. The mean duration of immobilization were 44.2 days in the group of immediate hip spica casting, and 65.1 days in the group of traction and casting. The radiologic examinations were performed 2 times and 6.9 times respectively. The clinical and radiological outcomes at the final follow-up were good in both groups. Insignificant leg length discrepancies were seen in 3 cases each group. The total charges of traction and casting was 2.4 times higher than that of immediate hip spica casting. CONCLUSION: The immediate hip spica casting seems to be an effective method of treatment in femoral shaft fractures without serious associated injuries under 10 years of age because there are several advantages such as satisfactory result, shortened hospitalization and immobilization, reduction of total charges, and lowered the risk of radiologic exposures.