The changes of Cadmium(Cd) in plasma, whole blood, erythrocyte and urine in Sprague-Dawley male rates exposed to intravenous single injection of 0.8 mg CdCl2/kg of body weight were investigated. Blood sample was taken at 0.5 to 672 hours, and 24 hour-urine was collected by using metabolic cage for the same period. The plasma level of Cd was reached to peak at 0.5 hour after injection and reduced rapidly in 1 hour. The Cd level in blood was the highest in plasma and the lowest in erythrocyte at 0.5 hour after injection. However, in one hour postinjection, the levels of Cd were higher in order of erythrocyte, whole blood and plasma, up to 4 weeks. The changes of urinary volume and creatinine were not significant between Cd-treated and saline-treated groups. However, urinary protein was slightly increased with time in Cd-treated group. Urinary Cd level was higher in Cd treated group than control. These results suggest that the measurement of Cd in erythrocyte and urine is valuable for the biological index to estimate recent Cd exposure.