The grafting of a mercaptoalkyltrialkoxysilane onto an activated poly(vinyl chloride) (PVC) paste resin with subsequent hydrolytic crosslinking has been studied. The resins were prepared by copolymerization of vinyl chloride monomer and glycidyl-methacrylate (GMA). The grafting of a mercaptosilane was carried out during gelation of the plastisol. In this step the formation of a chemical network was avoided. By steaming at 120 degrees C for 30 min the grafted samples crosslinked. The gel yield increased with increasing fraction of GMA and up to a given level with the fraction of the mercaptosilane. When using a resin of PVC homopolymer no crosslinking occurred. The silane grafted and crosslinked samples were found to have satisfactory thermal stability.