Several industrial applications of ionizing radiation are based on radiation crosslinking of polymers: crosslinking of wire and cable insulation, production of heat shrinkable materials, plastic foam, etc. Radiation induced crosslinking has been the subject of many studies, especialy the gel formation and effect of polymer structure and irradiation conditions on the yield of crosslinks. Much less has been done to study crystallization of crosslinked polymers in general and radiation crosslinked polymers in particular. It has been shown for example, that the total crystallinity in irradiated polyethylene is not affected except at very high absorbed doses. On the other hand it is significantly reduced in polypropylene and poly-l-butene already at doses about the gel point. In all cases remelting of irradiated polymers further reduced the total crystallinity.,In this work it is shown that not only the total crystallinity, but also the crystallization kinetics are affected by radiation induced crosslinks. The rate of crystallization indicated that the crystallization can be separated in two processes with different growth mechanisms. The rate of cooling is an important factor which determines the crystallization procedure and affects other properties dependent on crystallinity and morphology of crosslinked semicrystaline polymers.