The copolymerization of styrene (St) with N-vinyl carbazole (N-VC) was carried out in different solvents (benzene, ethyl acetate, acetone, or DMF) using alpha,alpha＇-azobisisobutyronitryle as an initiator at 60 degrees C. The copolymer compositions were estimated by elemental analysis. The monomer reactivity ratios of styrene (r(1)) and N-VC (r(2)) were determinated by Fineman-Ross and Kelen-Tudos methods and then recalculated using a nonlinear minimization algorithm based on the Mayo-Lewis method (RREVM). The reactivity ratios calculated by the RREVM method were found to be r(1) = 3.74, r(2) = 0.14 (benzene); r(1) = 5.02, r(2) = 0.11 (ethyl acetate); r(1) = 5.50, r(2) = 0.16 (acetone); and r(1) = 5.83, r(2) = 0.17 (DMF). The Alfrey-Price copolymerization parameters Q(2) and e(2) for N-VC in each solvent were calculated : Q(2) = 0.51, e(2) = -1.60 (benzene); Q(2) = 0.37, e(2) = -1.57 (ethyl acetate); Q(2) = 0.24, e(2) = -1.16 (acetone); and Q(2) = 0.23, e(2) = -1.17 (DMF).