When 7-radiation from W o interacted with fibrous cotton cellulose, the localization of at least part of the high energy resulted in cejlulosic chain cleavage and loss in breaking strength of the irradiated fiben. The substjtgtion of aromatic groups on the cotton cellulose molecule affected this localization of energy and decreased the radiation degradation of the fiber. The nature of the linkage of the aromatic group to the cellulose molecule was not as important as the radiation atability of the linkage. For example, if localization of energy occurred which cleaved the aromatic group from the cellulose molecule, the radioprotection of the cellulo$c molecular chain by the aromatic group WBR not effective. If the aromatic group was 80 modified that the effective number of electrons was decreased, the radioprotection of the cellulosic chain was also decreased. The radioprotection of the cellulosic molecular chain by benzhydryl, trityl, benzoyl, and cinnamoyl groups was effective over dista~~ces equivalent to several cellobiom units. The radioprotection of the cellulosic chain by naphthoyl groups was significant but not aa effective as the listed groups. Due to the sharing of -electrons in the naphthoyl group, the effective number of Hlectrons was reduced, and consequently the radioprotective effect of the group waa also reduced. Benzyl groups were cleaved from the cellulose molecule on irradiation and offered nq radioprotection to the cellulosic chain, at least at the high radiation doused. The ESR spectra of the irradiated celluloses, both substituted and unsubstituted, were similgr. This indicated that the presence of aromatic p u p s did not change the nature of the long-lived free radicals induced in cellulose on irradiation. It WM suggested thgt selective energy absorption by the aromatic group from the spur of high-energy electrons produced on interaction of y- radiation with the cellulose molecule could account for the radioprotection of the cellulosic molecular chain.