Radiolysis of polypropylene sulfide with thiol and thioether endgroups was investigated. The results of change in average molecular weight with radiation dose show that statistical main chain scission takes place (Gsc = 0.4–0.7). The following radicals could be identified by ESR-spectroscopy: A mechanism is proposed, which correlates the radical formation with chain scission. It can be shown that predominantly C? C bond scission and not C? S bond scission takes place.