Thirty-one growth-hormone-deficient dwarfs were re-examined after a period of 10 to 12 years. These subjects had initially shown glucose intolerance, insulinopenia and hyperlipidemia comparable to those of diabetic patients matched for age and sex, but vascular complications were not present in dwarfs. After 10 years glucose tolerance became progessively more abnormal in dwarfs than could be accounted for by expected deterioration with age, and hyperglycemia after mixed meals remained greater than in control subjects. Serum lipid and serum lipoprotein concentrations were abnormal in over one third of the dwarfs. Despite the metabolic similarity to the diabetic patients, clinical complications of diabetes were absent in dwarfs: retinopathy did not occur, and the prevalence of hypertension and arteriosclerosis was considerably lower in dwarfs than in the diabetic subjects in both study periods. The follow-up data support the hypothesis that growth hormone has at least a supportive role in the pathogenesis of vascular disease in the diabetic state.