Twenty-four weanling barrows were selected according to body weight and assigned to three dietary treatments: basal (0.6% Ca and 29 ppm Zn); basal + 0.6% Ca; and basal + 0.6% Ca + 71 ppm Zn. Unilateral neutron irradiation (268 rads) was administered to half of each treatment group. Twenty-four hours postirradiation, all swine were orally dosed with 0.5 mCi of 65 Zn. Whole-blood and plasma levels of 65 Zn were significantly lower in the irradiated animals for several days. In vitro uptake of 65 Zn by erythrocytes from the swine fed supplemental zinc was lower, but no differences were found in stable zinc in erythrocytes. Ad libitum feed intake was the same for all treatments, but average daily gain was lower in the irradiated swine. Radiation significantly decreased left kidney, liver, and spleen weights, heart weight, and hair growth. An absence of pigment was observed in the hair cortex on the side of the animal exposed to the reactor. Claudication of the left rear leg, facing the reactor, was observed in all swine. A significant lower value for weight and length in legs near the reactor was observed.