Assessment and treatment of limb-length inequality, particularly in the growing child, is a challenging task. Evaluation of the discrepancy requires an understanding of the significance of the disparity, as well as the natural history of the disorder, before formulation of a treatment plan. In the immature patient, consistent longitudinal data are essential to avoid pitfalls in the projection of ultimate length difference. Therapeutic options range from no treatment or use of a simple shoe lift to a surgical shortening or lengthening procedure. The current indication for lengthening is a disparity exceeding 5 to 6 cm. Epiphysiodesis or femoral shortening is useful for smaller discrepancies or for residual differences following a contralateral lengthening. Lengthening is done with a circular or cantilever external fixator, which may be combined with an intramedullary rod.