That the melt-mixed blend of poly (vinyl chloride) and acrylonitrile-co-butadiene rubber becomes crosslinked during high-temperature molding is evident from Monsanto rheometric, solvent swelling, and infrared spectroscopic studies. Dynamic mechanical analysis shows that such a self-crosslinkable plastic-rubber blend is miscible in different blend ratios. The degree of crosslinking depends on the blend ratios and the molding conditions. The cross-linking reaction involves the allylic chlorine sites in poly (vinyl chloride) and the CN group in the nitrile rubber. © 1993 John Wiley & Sons, Inc.