In the past, growth hormone (GH) deficiency has usually been diagnosed too late in dwarfed children, so that substitution therapy was not able to obtain a final height in the normal range for most of them. Complete catch-up of growth in hypopituitary patients needs early diagnosis and early treatment. This requires: (1) that full attention be paid to any insufficiency of length or height increment in infants and young children; (2) that evaluation of GH secretion be performed in spite of the practical difficulties encountered in small patients, and (3) that the interpretation of hormonal measurements be carefully discussed. Though the overall results obtained to date in treating very young GH-deficient children have not been completely satisfactory, it is certain that those whose height was within or near the limits of -2 SD at the onset of treatment maintained a normal height. The relationship of end results with the doses of GH used remains to be investigated. Future results will probably be improved more by earlier diagnosis and by using daily injections than by an increase in the annual dose of GH.