Ferrocene (Fc) was found to be an effective initiator for copolymerization of styrene (ST) with maleic anhydride (MAH). Copolymerization could be initiated by charge transfer complex formed between MAH as an electron acceptor and Fc as an electron donor. A good relationship between the formation of charge transfer complex and initiation activity was observed in the copolymerization of ST with MAH in various solvents. Overall energy of activation determined from an Arrhenius plot in dioxane was found to be 21.8 kJ/mol.