New bismaleimides (BMI’s) have been synthesized in the Bisphenol A (2e, 2k), terphenyl (3e, 3f), and tetraphenylketazine (4c) series. In three monomers, an additional functionality has been introduced with respect to conventional bismaleimides [viz., allyl (for 2k), N-maleimido (3f), and ketazine (4c)]; a new term, ’reactive building block" BMI’s, is introduced to describe such monomers. Cure profiles for new monomers have been determined by dynamic mechanical thermal analysis by supporting them on glass braids. Resins have been prepared on a multigram scale and have been studied by thermal gravimetric analysis for evaluation of thermal and thermooxidative stability.