Reaction rates for the Diels-Alder reaction of isoprene with maleic anhydride in the hexane-nitrobenzene mixed solvent were measured at 308.15 K. By using a reaction rate equation derived from the transition state theory coupled with the regular solution model, the reaction rates obtained previously at 293.88 K and in the present study were correlated. The dependence of reaction rates on the composition of hexane-nitrobenzene mixed solvent was correlated with fairly good agreement by introducing interaction parameters estimated with vapor-liquid equilibria into the regular solution model.