Fasciculate-re ticular slices of sheep adrenal cortex were incubated for 1 hr in Krebs-Henseleit solution containing glucose 5 mM and then for 3 hr in solution containing pyruvate-3-14C. Adrenal tissue from sheep treated for 1 week with triamcinolone acetonide, 0.1 mg/kg/day, showed a significant decrease in 14C incorporation into tissue cholesterol. A direct effect of steroids on adrenal lipid metabolism was studied by incubating adrenal cortical slices with cortisol sodium succinate 6.7×10−4m. The addition of cortisol was accompanied by a significant increase in 14C incorporation into medium bicarbonate and by significant decreases in 14C incorporation into fatty acids and cholesterol. ACTH in concentrations of 1.0 and 0.1 U/ml resulted in similar effects—increased 14C incorporation into medium bicarbonate, decreased 14C incorporation into adrenal cortical fatty acids and cholesterol. Modified pulse-labeling studies with acetate-2-14C revealed an early phase of disproportionate labeling of adrenal corti...