Eleven patients with idiopathic pituitary dwarfism were treated with KABI human growth hormone (HGH), and clinical effects on a linear growth and HGH antibodiesduring a course of a treatment were studied. The growth rate was 2.8 to 13.4cm/year in individual cases, and it was less than 5cm/year in 3 cases. One of them had a marked hypothyroidism and later thyroid replacement therapy increased a growth rate definitely. In other 2 cases, HGH antibodies were thought to be the cause of ineffectiveness. HGH antibodies with high titers were found in 4 cases before starting KABI HGH. All of those 4 cases had received Raben's HGH for 1 to 4years just preceding to KABI HGH. Antibody titers decreased after switching to KABI HGH in 3 of 4 cases and the restoration of growth was noted in 2 of them. On the contrary, in the rest of the cases, who were treated only with KABI HGH, no antibody developed in 3 cases and antibody of low titer developed in 4 cases. In these 4 cases no attenuation of growth was observed. From the above observations it is concluded that KABI HGH is clinically effective and much less antigenic than Raben's HGH.