Reactive oxygen metabolites can transfer, via oxygenation, the chemiluminigenic probes luminol and lucigenin to an excited state and thus induce light emission from these probes. This technique has been applied to a study of the effect of common food antioxidants on the availability of reactive oxygen species in aqueous model systems and in microsomal preparations. In all systems tested, propyl gallate and its congener octyl gallate proved to be the most active scavengers of the oxygenating species involved in the chemiluminescence reaction. In aqueous model systems, butylated hydroxyanisole was 10 times less efficient than the gallic acid ester antioxidants. In biological material, the lower scavenger activity of butylated hydroxyanisole is further compromised by its ability to induce a marked increase in production of hydrogen peroxide in the endoplasmic reticulum. Butylated hydroxytoluene is only marginally active in aqueous media and in biological material. It is concluded that gallic acid ester antioxidants may possess a significant protective potential towards toxic and carcinogenic agents due to their ability to remove toxic oxygen metabolites.