The hydrogen donating capabilities of antioxidants, such as butylated hydroryanisole (BHA), butylated hydroxytoluene (BHT), dl-α-tocopherol (Toc), sesamol and ethyl protocatechuic acid (EP), to a stable free radical, 2, 2-diphenyl-1-picrylhydrazyl (DPPH), were investigated. Toc, sesamol and EP donated two hydrogen atoms, BHA donated 0.75-1.2 hydrogen atoms, and BHT donated much less hydrogen. A synergistic effect on hydrogen donation to DPPH was observed with the combinations of Toc+BHT and BHA+BHT. The synergistic effect observed in the reaction between BHA+BHT and DPPH might arise from the regeneration of BHA from its oxidized intermediate, with the loss of BHT.