The foundation for the diagnosis of growth hormone (GH) deficiency in childhood must be auxology, that is, the comparison of the child's growth pattern to that of established norms for gender and ethnicity. It is only in those growing considerably more slowly than average that testing for GHD makes sense. Assessment of laboratory tests, whether static, for example, the measurement of growth factors or their binding proteins, or dynamic, for example, secretagogue-stimulated GH secretion is confirmatory. One must be cognizant of the assay used to determine GH, for there may be a 3-fold difference in the concentration of GH among commercially-available assays. Controversy still exists concerning the measurement of spontaneous GH release and whether sex-steroid priming is appropriate in prepubertal children. Imaging analysis may prove helpful in some children with congenital GHD or to detect a space-occupying lesion in the area of the hypothalamus and pituitary. The final diagnosis is based on multiple parameters and occasionally on a therapeutic trial of GH therapy to determine if there is a significant acceleration of growth velocity.