The metabolism of 65Zn was studied in 7 lactating goats after the administration of 100 - 200 uCi 65ZnCl-solution. 65Zn was detected in blood and milk 4 hours after the administration of the radio-nuclide. Maximum blood concentration was reached after about 24 hours and in milk after about 48 hours. At this time the concentrations was about 0.5 per cent per litre plasma or milk. The milk secretion of 65Zn accumulated during 7 days varied considerably. The 3 goats receiving 40 mg a day of dietary zinc secreted 2.7 - 5.8 per cent of the given amount of 65Zn, and the goats receiving 200 mg of stable zinc daily secreted only 0.3 -0.9 per cent. The accumulated urinary and faecal excretion showed less variation. The 4 animals studied excreted less than 0.2 per cent in the urine and 65.l - 91.4 per cent of the given amout in the faeces. The concentration of stable zinc ranged 690 -1070 ug per litre plasma and 680 - 1430 ug per litre milk.