Oxidant species are known to contribute to disease and dysfunction in biological systems. However, evidence has been progressively accumulating that demonstrates a more fundamental role for many oxidant species in the regulation of everyday function of healthy cells. Redox dependent signaling events involving the post-translational, oxidative modification of proteins has now been accepted as an important regulatory process, although the full extent of such mechanisms is yet to be determined. Some protein cysteinyl thiols are known to be susceptible to a number of redox-dependent modifications, including an interchange between the reduced thiol and several different oxidized disulfide states. Here, the role of oxidants as regulatory entities is reviewed, as are the many different ways protein disulfide formation can be analysed in complex protein mixtures. This includes an overview of many of the Proteomic strategies that can be used to identify proteins that form disulfides when pro-oxidizing conditions arise in cells, as well as related methods for studying intermediates that may precede disulfide formation.