Polyisobutylene, polystyrene, poly(vinyl acetate), poly(vinyl chloride) (I), mixed polymer of I and poly(vinyl Bu ether), chlorinated rubber, AlCl3, FeCl3, BF3, ZnCl2, SnCl2, SnCl4, CuCl2, and NiCl2 were added to asphalts (distilled, blown, and high-vacuum distilled) at 200-20°.The polymers containing no Cl gave mixtures showing little change in phys. properties.HCl formed by the decomposition of Cl-containing polymers and the metal chlorides caused an increase in softening point and a decrease in ductility.On the basis of viscosimetric and chromatog. data, this effect is ascribed to a catalyzed reaction (further accelerated by atm. O) which leads to a partial conversion of maltenes and resins into asphaltenes.AlCl3, FeCl3, and BF3 are the most effective catalysts.