The late results of treatment of 24 legs in 21 children with congenital deficiency of the tibia are presented. A new classification is proposed which correlates well with recommendations for treatment and with the final functional result. Three types of deficiency were recognised: Type I, total absence of the tibia; Type II, distal absence; Type III, distal deficiency with tibiofibular diastasis. The early radiographic appearances, the functional status of the quadriceps and the severity of flexion contracture of the knee were important factors in the selection of the operations likely to give the best function.