Three boys with growth hormone deficiency were given biosynthetic human growth hormone, four units subcutaneously three times weekly, over two years. All three exceeded their expected growth velocities for bone age during the first year, but fared less well during the second year. Mean yearly growth velocities were: 3.2 cms before treatment, 7.1 cms after 12 months' treatment and 4.9 cms after a further 12 months. There were no adverse reactions.