The purpose of this prospective study was to document results of early spica casting in treating all children aged 10 years or younger presenting during a 30-month period with a femoral shaft fracture. The outcome of 101 femoral shaft fractures thus treated demonstrated excellent results with few complications. Four spicas had to be removed at 7 to 10 days for unacceptable shortening and an additional four probably should have been. Control of alignment was not a problem, with only one patient's femur on cast removal being in a position different from that accepted at 7 to 10 days. An age older than 7 to 8 years is the only variable that might be used to predict the need for a change in treatment at 7 to 10 days.