Patterns of growth and development are presented for 33 patients with congenital posteromedial bowing of the tibia and fibula. The bowing is accompanied by shortening of the tibia and fibula, an initial calcaneovalgus deformity of the foot, and a decrease in ankle motion that does not improve with age. In general, the greater the initial bowing, the greater the ultimate extremity length discrepancy. The proportionate length differences between the normal and the bowed tibiae remained stable after the age of 12 months. This allowed a projection of anticipated extremity length discrepancy at maturity and a determination of the proper treatment. At birth the bowing varied from approximately 25 to 70 degrees, and at maturity the absolute tibial length discrepancies varied from 3.3 to 6.9 cm. Both the posterior and the medial components of the bow became markedly reduced with increasing age, but a mild residual medial portion of the bow remained. Soft tissue enlargement was observed in the posterior aspect of the affected legs in early life and developed to a relative muscle atrophy in later years.