This study tested the effect of Sigma antioxidant supplement®, α-tocopherol (vitamin E) and L-ascorbic acid (vitamin C) in the culture medium of bovine embryos. In experiment 1, in vitro produced bovine zygotes were cultured in Human Tubal Fluid (HTF) Eagles Basic Medium (BME) with Group 1 50 µm vitamin C; Group 2 200 µm vitamin E; Group 3 25 µm vitamin C and 100 µm vitamin E; Group 4 1 µl/ml Sigma antioxidant supplement®; and the Control group HTFBME only. In experiment 2, embryos were cultured in high or low oxygen tension with HTFBME + Sigma antioxidant supplement® or in HTFBME alone (Control). The data were analyzed using ANOVA followed by Tukeys test. The results of experiment 1 showed a negative effect (P < 0.05) of vitamin E on blastocystproduction in Group 2 (19.7 ± 0.1%). This effect was reduced in Group 3 by the addition of vitamin C (26.1 ± 0.2%). The use of vitamin C alone (34.9 ± 0.3%) or the Sigma antioxidant supplement® (33.3 ± 0.7%) did not increase (P > 0.05) the number of blastocysts produced compared with the control group (30.1 ± 0.5%). During experiment 2, there was no effect (P > 0.05) from the culture medium or the O2 concentrations used, indicating that the reduction of the O2 concentration did not improve blastocystproduction.(AU)