The purpose of this study was to determine the efficacy and safety of GH-releasing Hormone [GHRH-(1-44)] therapy in GH-deficient children. Twenty previously untreated prepubertal children with GHRH deficiency were treated for 1 yr in a multicenter, open label, company-sponsored study with at least 20 micrograms/kg GHRH-(1-44), sc, half at bedtime and half upon awakening. The main effects were enhancement of linear growth, advancement in bone age, and alteration in general blood chemistries and hormonal values. The mean velocity of the entire group increased from 3.6 +/- 1.1 to 8.1 +/- 1.5 cm/yr (P < 10(-4)) at 1 yr of therapy. After 6 months of therapy, 16 were growing at a mean of 9.4 +/- 2.0 cm/yr and were continued on this dose. In 4 patients who were growing at a rate of 5.5 +/- 1.7 cm/yr, the dose was increased to 40 micrograms/kg daily for the second 6 months. The high dose group increased their mean linear growth velocity for the second 6 months while on the higher dose to 7.6 +/- 0.4 cm/yr (P < 10(-2)). This was equal to the mean velocity for the second 6 months of therapy of the 16 subjects who remained on the 20 micrograms/kg daily therapy (7.6 +/- 1.2 cm/yr). Mean advancement of bone age was 1.3 +/- 0.6 yr during the first year of therapy. No adverse changes in general biochemical, hormonal, or pituitary radiographic analyses were noted. No change in fasting glucose or insulin concentrations, or excessive generation of insulin-like growth factor-I concentrations occurred. We conclude that GHRH in a daily dose of 20-40 micrograms/kg for 1 yr was effective in increasing growth velocity in most GHRH-responsive GH-deficient patients. It was well tolerated without side-effects. Glucose intolerance was not noted.