The absorption, storage and excretion of copper has been investigated in Merino sheep following intra-abomasal, intraruminal and intravenous administration of Cu-64. The excretion of the element via bile or urine is strictly limited. There is a most effective mechanism operating in the sheep which limits the intestinal absorption of the element when given in physiological or reasonable pharmacological doses. The absorption is increased to a certain threshold value in animals depleted of copper. In such animals administration of single abnormally large doses of copper does not force more copper through the intestinal mucosa. The ovine sheep liver clears administered copper rapidly from the blood stream and retains it avidly. Excess copper presumably previously loosely bound to albumin is rapidly eliminated by the kidneys. 35 references.