The aim of this retrospective study was to ascertain, whether an early growth hormone (GH) treatment can normalize height prognosis of children with congenital GH deficiency (GHD). The study covers 23 children with early onset GHD who received GH 0.1 U/kg/day from the beginning of therapy (0.4-4.9 years). This dose was corrected for weight every 3 months during the whole duration of treatment (mean 7.9 +/- 2.4 years). As a consequence of the significant growth acceleration induced by GH treatment, the patients' height deficiency at the last check had changed from a range of between -8.0 and -1.8 SDS to between +0.5 and -4.3 SDS; on the average, it was significantly less severe than before treatment. Satisfactory growth acceleration was achieved in most patients concomitantly with accelerated bone maturation, as was shown by the stable height age/bone age ratio observed during the follow-up period. The predicted ultimate height was significantly greater than the pretreatment height and it did not differ from the target height. It is concluded that catch-up growth to the target percentile in GHD patients is possible, provided that substitutive treatment is begun during the first years of life and that GH doses are adjusted periodically for weight changes.