Six newly weaned karakul ewes, three with fat tails and three without tails, were used to investigate the metabolic and hormonal changes during accelerated growth. Two lambs acted as controls, while the remaining four were Subjected to a maintenance diet for two weeks. The subsequent resumption of ad lib feeding caused a period of accelerated growth for approximately four days before the normal growth pattern resumed. Blood samples were drawn from surgically implanted catheters in the caudal aorta and vena cava during normal growth, maintenance (zero) growth and accelerated growth. These samples were assayed for glucose, free fatty acids, glycerol, alanine, lysine, growth hormone, insulin and thyroxine. It was found that during the period of accelerated growth, glucose concentrations decreased after feeding while free fatty acids and glycerol concentrations increased after feeding. This is the inverse of the normal growth pattern. The uptake of lysine was doubled during accelerated growth, while alanine concentrations did not change significantly. Growth hormone concentrations dropped during accelerated growth and increased dramatically during the subsequent normal growth phase, while insulin concentrations increased during accelerated growth. Thyroxine concentrations increased during accelerated growth and dropped during the subsequent normal growth phase.