It has been known for more than 30 years that growth hormone has a lipolytic properties and growth hormone excess (acromegaly) and growth hormone deficiency have been reported to be associated with abnormali ties in serum lipoprotein concentrations. Due to the lipolytic effect of growth hormone, its administration in man has been reported to increase plasma nonesterified fatty acid (NEFA) concentrations. Ketone body production increases during acute growth hormone excess as a result of increased NEFA concentrations; similarly, the increase in serum triglycerides may be explained by an increase in substrate (NEFA) supply to the liver for VLDL production. The effect may be enhanced by a simultaneous decrease of serum lipoprotein lipase activity. The cholesterol-lowering effect of growth hormone administration has not been investigated in detail, specifically, the effect of growth hor mone on LDL kinetics is unknown. Growth hormone-excess and growth hormone deficiency have been reported to be associated with increased risk for atherosclerosis; an association with serum lipoprotein changes is likely but evidence for a causal link is yet lacking.