A prospective study of femoral shaft fractures in children less than 14 years old has been practised in 71 patients annually revised clinically and radiographically. Processing of data has been carried out with multivariate models. Femoral overgrowth (SF) averaged 8'63 mm. (range 1-21), and was found to be influenced by: age (greater SF in children between 3 and 9 years); initial displacement of fracture-fragments (greater SF in fractures severely displaced), and overriding of the fragments at time of healing ( overriding diminish overgrowth). SF was a universal phenomenon that occurs fundamentally along the first year of evolution, extending in the 27 per cent of the cases until the fifth year of evolution; from this moment, the growth speeds of both femurs were equalled in ali cases. Ipsilateral tibial overgrowth ocurrs only in 45 per cent of the patients and average 0'65 mm. (1-5). Angulations in frontal and sagital planes tended to correct totally if they were under 10º on the first plane and 15º on the second, regarding physiological values. Malrotations were not very frequent, being influenced by treatment and level of fracture. It seems they have a tendency to correct with growth.