Growth hormone-releasing hormone (GHRH) when given s.c. to GH-insufficient children either as pulses, or once or twice daily, promotes linear growth. These treatment regimens, however, are not ideal as they require frequent drug administration and a significant proportion of patients do not show improved growth. We have now investigated the GH response to a nocturnal s.c. infusion of GHRH (1-29)NH2, at two dosages, 5 and 10 micrograms/kg/h, in a group of five GH-insufficient children. The s.c. infusion of GHRH between 2100 h and 0600 h augmented nocturnal pulsatile GH release in all five children. There was a dose-dependent response for the GH area under the curve (AUC), and mean total GH concentration. The AUC for GH was significantly greater after the 10 than 5 micrograms/kg/h GHRH which in turn was greater than that after placebo; mean (SD) AUC: 14816 (3978), 8125 (1931), 3032 (1582) mU min/l respectively (P less than 0.01 and P less than 0.05). There was no significant change in the number of GH pulses during the 9-h infusions when the subjects were infused with GHRH 10 or 5 micrograms/kg/h compared to placebo, and they occurred at similar times although the number of pulses tended to be greater after GHRH; the mean (SD) numbers of GH pulses were 5.0 (0.7), 3.8 (0.8), 3.2 (0.8), respectively. There was however a significant rise in the mean baseline GH concentration in all patients during the infusion of GHRH 10 micrograms/kg/h compared to placebo, but not with 5 micrograms/kg/h. Thus, GHRH(1-29)NH2 given s.c. augmented nocturnal pulsatile GH release in GH-insufficient children but it also increased baseline GH secretion. These results suggest that a sustained release preparation of GHRH could be a potential treatment for GH-insufficient children, and that a dose of 5 micrograms/kg/h would promote pulsatile GH release, but that at higher dosage it may also raise basal GH secretion.