Up to now, the end results of treatment in GH deficiency (GHD) have not been as good as expected. Probably the main cause has been the delay in diagnosing GHD in short children, resulting in a very insufficient height at the onset of puberty. The need for early diagnosis and treatment must be emphasized. This agrees with the well-documented data demonstrating (1) that catch-up growth obtained in any treatable growth disorder has a limited duration, and (2) that the effect of GH replacement, whatever the doses and modes of therapy, is maximal during the first year and wanes during the following years. There are still many questions regarding the appropriate GH replacement dose. The height gain during the first year of treatment has been correlated with the logarithm (decimal or natural) of the dose in several groups of patients receiving GH 3 times/week. The initial dose-response relationship is better with GH 6 times/week. For the following years, no dose/response ratio has been demonstrated, and the final height-to-dose relations are still to be investigated. A dose increase after 2 years or more may improve the growth rate, but also with secondary waning. Thus, long-term prospective dose-response studies are needed. The first period of one such study is presented.(ABSTRACT TRUNCATED AT 250 WORDS)