In a double-blind study 12 prepubertal children with idiopathic growth hormone (GH) deficiency were treated with growth hormone releasing factor (GRF) 1-44 in a dosage of 7.5 or 15 micrograms/kg body weight, administered once a day subcutaneously. With 7.5 micrograms/kg the average growth velocity increased from 2.5 to 4.6 cm/year, an insufficient response. With the higher dosage the average growth velocity increased from 2.7 to 7.0 cm/year, a similar increase as observed with GH therapy in subsequent periods. In 3 of the 6 children treated with the higher dose appropriate catch-up growth was observed. The growth response of the lower leg length was not always consistent with the statural growth response.