The aim of this study, performed in 10 children, was to verify if a treatment schedule, better reproducing the growth hormone (GH) physiological pattern, could achieve a greater growth response than daily s.c. administration in previously successfully treated children with an isolated idiopathic GH deficiency. A 1-month washout period was observed between the previous regimen and this study. GH (0.6 U/kg/week, the same as given previously) was administered weekly in 6 equal doses. Three children received the daily dose by a single s.c. administration (at 20.00 h) and the other 7 through a 27-gauge infusion needle inserted s.c, using a mini infusion pump permitting a constant delivery of 50% of the daily dose (20.00-08.00 h) and the administration of the other 50% through 3 equal pulses (at 20.00, 24.00, and 04.00 h). After 6 months each child changed regimen undergoing the other one with a 1-month washout interval. During the 12 months of therapy, the mean height increased from -3.2 (SE 0.45) to -2.8 (SE 0.37) SDS. When evaluating the circulating insulin-like growth factor-I pattern as well as the growth velocity and the ratio bone age increase/height age increase, no differences were noted between the two treatment regimens.