Oxidative stability of muscle from broilers fed 1) basal feed; 2) basal feed supplemented with 100 mg of a mixture of natural source RRR-alpha-,gamma-,delta-tocopheryl acetate/kg feed; 3) basal feed supplemented with 100 mg of synthetic all-rac-alpha-tocopheryl acetate/kg feed; 4) basal feed supplemented with 500 mg of a mixture of natural source RRR-alpha-,gamma-,delta-tocopheryl acetate/kg feed; or 5) basal feed supplemented with 500 mg of synthetic all-rac-alpha-tocopheryl acetate/kg feed, was evaluated during chill and freezer storage by determination of thiobarbituric acid reactive substances (TBARS). The oxidative stability of precooked muscle was investigated in a chill storage experiment and in a model system with accelerated oxidation. The basal feed contained a standard added amount of 46 mg all-rac-alpha-tocopheryl acetate/kg feed. Furthermore, the basal feed had a high natural content of vitamin E, resulting in a dietary vitamin E level in the control feed of 72 mg alpha-tocopherol and 69 mg gamma-tocopherol, a level that provided a reasonable oxidative stability for the meat. In spite of this, raising the dietary vitamin E level resulted in improved oxidative stability of broiler muscle during storage. Supplementation of broiler feed with 100 mg all-rac-alpha-tocopheryl acetate/kg, resulting in a total alpha-tocopherol content of 198 mg/kg feed, was found to be sufficient to improve stability of precooked broiler breast and precooked thigh muscles during chill storage, and further to ensure stability of raw meat during chill and freezer storage. The mixture of natural source RRR-alpha-,gamma-,delta-tocopherol was less effective in protecting broiler muscles than the synthetic all-rac-alpha-tocopherol, when compared on a weight basis.