A total of 24 sheep were used to study two routes of vitamin E administration: intraruminal (IR) and intraduodenal (ID). For each route of administration, 12 sheep were divided into 3 groups of 4, and each group received one of the following vitamin E treatments (mg/kg body weight): treatment 1, D-alpha-tocopherol (60 mg); treatment 2, D-alpha-tocopherol acetate (70 mg); treatment 3, DL-alpha-tocopherol (90 mg). The results showed that two major indices of bioavailability, i.e. concentration maximum and the area under the plasma concentration time-curve, were higher following IR administration than ID administration for all three vitamin E compounds used in this experiment. In sheep dosed intraruminally no difference was observed between the three vitamin E preparations in their plasma vitamin E response. For the ID administration the peak of plasma vitamin E concentration was lower after D-alpha-tocopherol acetate dosing than with the other two preparations. The results indicated a beneficial effect of rumen environment on the availability of vitamin E supplements.