The blood levels, toxicokinetics and urinary excretion of selenium were investigated in healthy male buffalo calves after single oral and intravenous administration of selenourea at the dose rate of 0.75mg/kg (providing 0.48mg/kg selenium). The concentration of selenium in blood and urine was estimated spectrophotometrically. Following administration of the drug, the blood selenium disposition patterns exhibited two distinct peaks. The toxicokinetic parameters of selenium were determined by employing non-compartmental analysis. The values of AUC, t(1/2elm), Cl(B) and Vd(SS) were 18.46μgml(-1)h, 10.33h, 20.04mlkg(-1)h(-1)and 0.3lkg(-1), respectively, after oral administration and 23.97μgml(-1)h, 7.12h, 20.53mlkg(-1)h(-1) and 0.2lkg(-1), respectively, following intravenous injection of selenourea. The value of MRT was higher after oral dosing. The bioavailability of selenium, following oral administration of selenourea was 77%. Approximately, 22% of the total intravenous dose and 5.9% of total oral dose of selenium was excreted in urine within 24h of administration of selenourea. The data on blood Se levels may be of help in diagnosing the impeding selenium toxicosis and thus preventing mortality due to selenium toxicity.