In a study conducted in 1969 and 1970 lactating cows were given oral or intravenous (I.V.) doses of radiotungsten. Blood, milk, urine and feces were collected and analyzed to measure transfer rate and quantity of tungsten eliminated over an extended period during and after exposure. The average per cent of administered dose secreted per liter of milk at peak activity was 0.01 and 0.1 for the groups receiving oral and I.V. doses, respectively. During the 84-hr period after dosing, 79% of the orally administered dose was recovered, with 64% recovered in the feces, 14.6% in urine and 0.4% in milk. In the same time period, 68% of the intravenous dose was recovered with 65% in urine, 2% in the milk, and less than 1% in feces. Tissue distribution results indicate the principal sites of short-term radiotungsten deposition were skin, liver and soft tissue. Long-term retention sites in mature cows were bone, muscle and skin. Long-term retention sites in calves were bone, adrenal, skin and spleen.