The cationic polymerization of styrene initiated by arsenic trichloride (AsCl3) in the presence of traces of acetic acid (co-catalyst) at -8, -4, and 0°C for 100 min using the dilatometric technique in an inert atmosphere yielded low molecular weight polymer. The rate of polymerization (Rp) is a direct function of the concentration of AsCl3, monomer, and polar solvent, but inversely proportional to the polymerization temperature and nonpolar solvent. Hydroquinone has no effect on RpVarious kinetic parameters have been evaluated and a kinetic scheme is proposed.