Cationic Polymerization of a- methylstyrene was carried out in chloroform by using H2SO4 as catalyst. The effect of temperature, monomer and catalyst concentrations were studied. The dependence of the initial rates on the initial monomer [M]o and catalyst [C]o concentrations is - d [M] /dt = k [M] 0 [C] o for chloroform solution. On the other hand, rate of polymerization increases to a certain temperature and then decreases. It was found that molecular weight of the polymers increases with the monomer con- centration and temperature, but it isn’t dependent on the catalyst concentration.