Reactive oxygen species represent a common mediator of environmental stress such as during physical exercise, ozone exposure, UV radiation and xenobiotic (pollutant) metabolism. Antioxidant defense systems protect against the ravages of such reactive species. In contrast to the conventional idea that reactive oxygen is mostly a trigger for oxidative damage of biological structures, now we know that low physiologically relevant concentration of reactive oxygen species can regulate a variety of key molecular mechanisms that may be linked with important processes such as immune response, cell-cell adhesion, cell proliferation, inflammation, metabolism, aging and cell death. Oxidation-reduction (redox) based regulation of signal transduction and gene expression appears to be a fundamental regulatory mechanism in cell biology. The talk will address the regulation of transcription, apoptosis and cell-adhesion by redox processes and will explore, in light of that knowledge, the emerging potential of thiol antioxidants.