The authors analyse 21 patients with congenital inequaliti of the lower limbs that had been included on a lengthening programme. The shortening aetiology was: global hipoplasy (8p), congenital deficiency of the fibula isolated (5p) or associated to proximal femoral focal deficiency (PFFD) (3p), congenital short femur (3p) and congenital abscense of the tibia (2p) The authors evaluate the anticipated discrepancy at the end of growth, the lengthening that was obtained and the complications that had been arised. On the femur and tibia hipoplasy the authors equalize the length of the lower limbs in the 75% of the patients, at only one time of lengthening. On the aplasya of the fibula the authors require two periods of lengthening and the achievement of complementary orthopaedic surgery. The authors conclude that the decision to initiate a limb lengthening programme must include not only the leg inequality evaluation, but also anothers factors like the associated anomalies, joint inestability, axial disturbance, foot condition, joint and muscle balance and the patient and family collaboration.