The modification of proteins by HOCl seems to be a highly complex reaction. Data describing this process are available mainly based on the structure analysis of modified amino acids or peptides at low HOCl concentration. In a report by Salavej et al. [31] , HSA was treated with HOCl at a 25-fold molar excess, similar to the procedure by Pattison et al. [18] . In their analysis, oxygenation was detected for Trp238, Met147, Met353, and Met572, but no chlorination of any of the HSA residues was detected. Using HOBr, Salavej and coworkers detected the incorporation of one or two bromines at Tyr425, but no chlorination of any HSA residues was detected in HOCl treated samples [31] . However, the treatment of amino acid residues with HOCl leads to the documented side chain modifications, but HOCl-modification seems not to be limited to these side chain products. In the context of a linear peptide or protein HOCl-modified side chains undergo intra-or inter-molecular cross linking. Thus, in the context of a complex protein and probably under conditions with excessive concentrations of HOCl, the process is pushed towards the development of complex protein conformations the nature of which is still unknown. One final product of HOCl-treatment seems to be the generation of stable antigenic epitopes on human serum albumin.