The invention is based on the discovery that a remarkable improvement in the performance of maleimide thermosets can be achieved through the incorporation of imide-extended mono-, bis-, or polymaleimide compounds. These imide-extended maleimide compounds are readily prepared by the condensation of appropriate anhydrides with appropriate diamines to give amine terminated compounds. These compounds are then condensed with excess maleic anhydride to yield imide-extended maleimide compounds.