An 11 year old Austrian boy with isolated growth hormone deficiency type I A is described. On institution of GH therapy at the age of 2 2/12 years there was only a short growth response and anti-GH-antibodies with high binding capacity were detected, and growth was inhibited. Examination of the nuclear DNA by restriction endonuclease analysis demonstrated a defect of the GH-N gene in the patient. The results suggest the deletion in this Austrian family is different from that seen in other patients. The parents were heterozygous for the deletion and had a subnormal GH response to stimulation with arginine, but their somatomedin-C concentrations and their heights were normal. The patients' sister was of normal height, hormone analyses were normal, and the GH-N gene was not affected.