In 1967 the first patient in Northern Ireland commenced growth hormone treatment for short stature. By the end of December 1988 a total of 89 patients had been treated. Thirty-two had idiopathic isolated growth hormone deficiency, an incidence of 1.5 new cases per year (in a population of 1.5 million with approximately 30,000 births per year). Since 1967 the mean age at starting treatment has fallen from 18 years to 10 years and the height standard deviation score has fallen from -4.7 +/- 0.6 to -3.4 +/- 0.3. The group with classical growth hormone deficiency (maximum GH less than 7 mU/l during insulin-induced hypoglycaemia) had a greater increase in height velocity over the first year of treatment, 3.8 +/- 0.4 cm, than those with a partial deficiency (maximum growth hormone 7.1 - 20 mU/l), 1.9 +/- 0.4 cm. All pre-pubertal children responded with a rise in the height velocity standard deviation score from -1.8 +/- 0.3 before treatment to +3.5 +/- 0.4 over the first year of treatment. 58% of the adult males and 25% of adult females have attained an adult height within the normal range (3rd centile or above). There have been three deaths, one each from Fanconi's aplastic anaemia which predated growth hormone treatment, an accidental fire injury and a relapsing craniopharyngioma. There have been no deaths from Creutzfeldt-Jakob disease. Growth hormone therapy is safe and effective, but continues to be commenced late in terms both of age and height standard deviation score.