A penultimate model of acrylate polymerization has been proposed to account for reduced reactivity of radicals formed by monomer addition to midchain radicals. New expressions derived for polymerization rate, number-average degree of polymerization and branching level are used for a comparative analysis of the penultimate and terminal models. The penultimate model has been also implemented into the simulation program PREDICI to conduct a comparative analysis of time dependencies of conversion, cumulative number-degree of polymerization and cumulative branching levels calculated for the different models. The calculations show that, depending on radical reactivity ratio si and monomer concentrations, the predictions from the penultimate model significantly deviate from those of the terminal model.