Ruminants meet their energy requirements primarily from volatile fatty acids produced by rumen micro—organisms. It has been shown that several of these fatty acids are potent insulin secretagogues both in vivo and in vitro. In the present studies the influence of the plasma free fatty acid level on growth hormone (GH) secretion was investigated in sheep using a variety of antilipolytic agents such as 3,5–dimethyl pyrazole, nicotinic acid, salicylate, and insulin. Inhibition of fat mobilization by these compounds was invariably associated with highly significant elevations of plasma GH levels. This response was correlated with the degree of starvation and the accompanying elevated plasma free fatty acid level and was inhibited by the intravenous infusion of acetate, propionate or a combination of triglyceride and heparin. Dimethyl pyrazole or nicotinic acid failed to elicit a rise in plasma GH during the intravenous infusion of epinephrine (0.5 μg/kg/min) despite a precipitous fall in FFA levels, confirming earlier observations on epinephrine inhibition of GH secretion. It is concluded that the plasma FFA level plays an important role in GH homeostasis in the ruminant. (Endocrinology92: 402, 1973)