The impact of dietary vitamin A, E, and C concentration on rate and efficiency of body weight gain and serum vitamin E (a-tocopherol) concentration was determined in pigs experiencing a low or high level of antigen exposure (AE). Pigs were reared via two management schemes that resulted in either a low or high level of AE. Dams of the pigs received a corn and soybean meal diet devoid of supplemental vitamins A, E, and C from day 60 of pregnancy through lactation. Postweaning, pigs were individually penned and self-fed a basal diet containing 25% of the estimated requirement (1) for 11–22 lb pigs for vitamins A and E, and 3.64 mg of vitamin C per pound of diet. At 21±2.6 lb body weight, pigs within a litter were randomly allotted to the basal diet supplemented with vitamins A, E, and C equivalent to 0, 100, 200, 300, and 400% of NRC (2 mg of C added per 1 IU of E). Low AE pigs had lower serum alpha-1 acid glycoprotein concentrations (466 vs 726 mg/mL) indicating they experienced a lower level of AE. Low AE pigs also gained body weight faster (1.39 vs 1.27 lb/day) and required less feed per unit of gain (1.37 vs 1.45) than high AE pigs fed from 21 to 55 lb body weight. As dietary concentrations of A, E, and C increased, daily gains increased quadratically, but the magnitude of response was greater for the high AE pigs. Serum vitamin E concentrations increased with increasing dietary concentrations of vitamins A, E, and C in low AE pigs but remained constant in high AE pigs. Based on these data, dietary needs for one or more of vitamins A, E, and C are greater in pigs experiencing a high versus low level of chronic antigen exposure. Furthermore, the needs of high-antigen-exposed pigs are greater than current estimated requirements (1).