In contrast to the sustained acceleration of growth observed in pituitary hypersecretion in GH, full catch-up growth is rarely attained in GH deficiency with conventional GH Rx (0.1 U/kg IM 3x/wk). Since circulating GH levels are very low for all but 24-30 hr per wk during conventional Rx, we examined the feasibility and metabolic effects of CSIGH using a small infusion pump. Somatomedin-C (SM-C), oral glucose tolerance (GT) and free fatty acids were determined in 7 untreated deficient children before and after 85 hrs of CSIGH (2.1 μU/kg/hr ≃ 0.3 U/kg/wk). CSIGH maintained serum GH at 3-9 ng/ml and produced a modest increase in fasting (0 min) G and I. Glucose tolerance was impaired despite 2-fold higher I levels (*p