The growth response to 6–12 mg/week of human growth hormone (HGH) administered for 2–5 yr was observed in 15 growth hormone deficient patients 2–17 yr of age at the time of initial treatment. Growth rates of 8.4–15.9 cm/yr were seen during the first 3 or 4 months of therapy in children who did not receive concurrent cortisone acetate. These rates were 2–5 times greater than those observed during pre- or post-treatment periods. In 8 patients, annual rates for the entire first year of treatment were 2 cm or more less than these initial values. Fourteen of the 15 maintained a normal growth rate (5 cm or more per yr) during the second yr. Seven patients were followed during a third yr of HGH administration and all continued to grow normally. One child has been treated for an additional 2 yr and has continued to respond. No advantage was found with daily or once per week schedule of hormone administration. In children maintaining a growth rate of 6 cm or more per yr, gains in height exceeded concomitant advances in skeletal maturation. It was concluded that highly purified, nonantigenic preparations of HGH (Raben), in doses of 6–12 mg/week, provide effective longterm therapy for most growth hormone deficient children.