a- Methylstyrene was polymerized in the pur and mixed solvents, using sulphuric acid as catalyst. Rate of polymerization increased as dielectric constant of the solvents increased. The molecular weight of poly a- methylstyrene did not change in the pur and mixed sol¬vents. It was also seen that the plots of log Rp against D and (D-l) /(2D + 1) gave the straight lines.