The objective of this study was to optimize the character of the unshrinkableness of wool fibers. A study of the processing of fibers of wool by an oxidative processing by performic acid was carried out by a complete factorial design to determine the most influential parameters of this study and then to optimize this process by the method of simplex. In parallel, a new ozone treatment was applied and a central composite design adapted to this protocol made it possible to identify the most influential parameters. This last type of processing has the advantage of being less polluting. (C) 2003 Wiley Periodicals, Inc.