The reaction of Wool with a disulfide-containing crosslinking agent, i.e. bis(${eta}$-isocyanatoethyl) disulfide (BIED), was studied in an attempt to obtain disulfide-enriched wool. BIED was reacted with wool both monofunctionally and bifunctionally to from branches and crosslinks, respectively. The crosslinking efficiencies in the percent ratio of the number of the crosslinks formed to the total disulfide introduced, which were obtained before and after reduction, ranged from 37% to 68%. The setting behaviors of several samples such as BIED-treated, untreated, hexamethylene diisocyanate-treated, and butyl isocyanate-treated wool were studied under the absence and the presence of a reducing agent. Rearrangement of secondary bonds faciliated by cleavage of crosslinks as well as rearrangement of crosslinks itself seems to play an important role in the set stability.