In this study a -methy styrene has been polymerized in the presence of sulfuric acid. The effect of polymerization time, temperature, monomer concentration on the rate of polymerization and molecular weight of the polymer were investigated. a -Methyl styrene was polymerized at five different temperatures (-40°C, -50°C, -60 °C, -70°C, -78 °C) and it wâs obcerved that the molecular weight of the polymers increases as the temperature decreases. On the other hand, rate of polymerization increases to a certain tempe¬rature and then decreases. The relation of the limiting viscosity number and temperature was found as log [vj] = 0.698 X 10’ X —1 : 4.0626 It was found that the molecular weight of the polymers does not change by changing the polmerization time. a -Methyl styrene w as polymerized taking different monomer concentration. It was found that as the monomer concentration increases rate of polymerization and deg- ree of polymerization increase. Rate of polymerization changes with the second power of mono¬mer concentration. It was concluded that termination with chain transfer to monomer does not take place.