The objective of this study was to compare the effect of 2 esters of alpha-tocopherol, all-rac-alpha-tocopherol acetate and RRR-alpha-tocopherol succinate (d-alpha-TOS) on growth and immunity in broiler chicks. Three hundred twenty 1-d-old commercial Arbor Acres broilers were randomly distributed to 4 treatments, each of which had 8 pens of 10 chicks per pen. Birds in the control group were fed with the diets supplemented with 30 mg/kg of all-rac-alpha-tocopherol acetate or the basal diet with d-alpha-TOS supplementation at 10 mg/kg (TOS1 group), 30 mg/kg (TOS2 group), and 50 mg/ kg (TOS3 group), respectively, for 42 d. The results showed that there was no significant difference (P > 0.05) in BW gain, feed intake, or G:F among the treatments. Significant positive correlations existed between dietary supplemental alpha-TOS levels and plasma (R(2) = 0.9831, P < 0.01) or hepatic (R(2) = 0.9336, P < 0.05) alpha-tocopherol concentrations and a negative correlation with plasma (R(2) = 0.9487, P < 0.05) or hepatic (R(2) = -0.9901, P = 0.0518) malondialdehyde levels. The concentrations of serum glutathione (GSH) were highest at 50 mg/kg at 42 d of age (P < 0.05), and hepatic GSH was significantly higher at 30 and 50 mg/kg compared with the other groups. Marked enhancement of splenic T- and B-lymphocyte proliferation occurred in group TOS3 as compared with the other groups. The study suggests that the immunoenhancement effect observed in broilers fed additional d-alpha-TOS between 30 and 50 mg/kg might result from increased retention of alpha-tocopherol and reduction in lipid peroxidation, as evidenced by the decrease in malondialdehyde and the increase in GSH.