Fifteen short but otherwise normal children, 4.3 to 15.5 years old, with heights greater than 3 S.D. below the mean value for age, growth rates less than or equal to 5.0 cm per year, and normal serum levels of immunoreactive growth hormone in response to provocative stimuli (peak greater than or equal to 10 ng per milliliter) were treated with intramuscular injections of pituitary growth hormone (0.1 U per kilogram) three times weekly for six months, as were 14 children with documented growth hormone deficiency. In all the latter children growth rate increased by more tan 2.0 cm per year during treatment. In 6 of the 14 short normal children who remained prepubertal, growth rate also increased, by 2.2 to 4.2 cm per year during treatment; four of these children had normal base-line serum somatomedin C concentrations. In both short normal children and children with growth hormone deficiency, the increment in serum somatomedin C concentrations after 4 or 10 daily injections of growth hormone correlated with bone age but not with later growth or growth hormone levels. Among the short normal children, those who responded to growth hormone were younger and had a greater delay in bone age and a slower pretreatment growth rate than the nonresponders. These observations suggest that a dose of growth hormone comparable to that used for the treatment of hypopituitarism increases growth rate in some short normal children.