The rates of free-radical initiated alternating copolymerization of alpha-methylstyrene with N-alkylmaleimides (RMI) decrease in the following order : Me>Et>n-Pr almost-equal-to n-Bu almost-equal-to n-Hex>iso-Pr> tert-Bu. A linear relationship was established in the plots of log (k(R)/k(Me)) against polar substituent constants sigma*, "true steric" factors E(S) and corrected steric factors E(S)C. The best fit was obtained in plots of log (k(R)/k(Me)) against sigma* and E(S)C while a large scattering of results was observed in the plot of log (k(R)/k(Me)) against E(S).