SYNOPSISPaediatricians are giving increasing attention to the assessment of developmental status in addition to size. The skeletal age of the hand or knee is often determined in such an assessments. This is a useful guide to the maturity of the whole skeleton because it is unusual for separate parts of the skeleton to differ greatly in maturity. There is evidence that assessments of skeletal age are sufficiently reliable for both clinical and research purposes if the assessors are trained adequately. These assessments can be useful in the clinical management of growth disorders, endocrinopathies and inequalities of leg length.