Relative bioavailabilities of four chemical forms of vitamin E were evaluated when supplemented in diets of finishing swine for 28 d. Forty crossbred pigs (80 kg), individually penned, were divided equally among five treatments. Treatments consisted of corn soybean meal-based diets supplemented with DL-alpha-tocopherol, DL-alpha-tocopheryl acetate, D-alpha-tocopherol, or D-alpha-tocopheryl acetate. A treatment without vitamin E supplementation (negative control) served as the fifth treatment. Each compound was supplemented at 62 IU/kg of diet. Blood samples were collected on d 0, 1, 2, 7, 14, 21, and 28. On d 29, half the pigs were slaughtered to obtain tissue samples. Feed samples, taken from feeders, were also collected on d 0, 5, 14, and 21. All vitamin E forms fed increased (P < .01) serum alpha-tocopherol by d 2 and peaked by d 7. Serum alpha-tocopherol in pigs fed either acetate form remained elevated beyond d 7; serum alpha-tocopherol steadily declined and was lower (P < .01) on d 14, 21, and 28 in pigs fed either alcohol form compared with concentrations in the acetate-fed pigs. The decrease was probably a reflection of poor stability of the alcohol forms observed in the feed; the acetate forms were found to be stable in the feed over the 28-d study. Dietary supplementation of D-alpha-tocopheryl acetate resulted in the highest serum alpha-tocopherol throughout the study. A similar trend was observed in tissue (liver, backfat, leaf fat, semimembranosus, rhomboideus) alpha-tocopherol and serum: the liver had the highest concentration.(ABSTRACT TRUNCATED AT 250 WORDS)