Twenty-four gravid cross-bred heifers were maintained on conventional cottonseed hull, corn, soybean meal rations and killed at 90, 180 or 270 days gestation for maternal fetal tissue analyses. Fifteen of these heifers were dosed orally or intravenously with Zn65 for 24, 96 or 168 hr. blood-balance study previous to sacrifice. Cows consuming 28 ppm zinc absorbed 22±5%, excreted 4.3±0.4 mg./day in the urine and transferred 5.8 mg. zinc to the fetus during the first 90 days of pregnancy. Fetal zinc increased 13 times between trimester 1 and 2 and another 7 times during the final trimester. Pregnancy effects were not observed either on blood or fecal excretion patterns nor upon maternal tissue zinc concentration values. Both total and absorbed radiozinc were highest in liver, pancreas, muscle, kidney, spleen and adrenal, in that order for soft tissue. Zinc concentrations in ribs, femur and mandible equaled that for liver. Maternal tissue Zn65 levels, after 168 hr., showed significant increases at each trimester, and fetal liver and bone Zn65 values usually exceeded those of the dam. Maternalfetal tissue Zn65 values from cows killed after 24, 96 and 168 hr. after intravenous dosing showed deposited maternal liver Zn65 to decrease markedly at each period, while fetal liver and bone values tripled. Calculated partition of radiozinc in third trimester cows and products of conception indicated that after seven days 86.3% of that Zn65 absorbed was retained by the dam, and 13.7% was transferred and deposited in the total fetus (58.7) placenta (40.9) and fluids (0.4).