The cure kinetics and mechanisms of a diaminodiphenylsulfone-cured tetraglycidyl-4,4’-diaminodiphenylmethane epoxy and its blends with poly(ether imide) (PEI) of various compositions were studied using differential scanning calorimetry (d.s.c.). An autocatalytic mechanism was observed for the epoxy-PEI blends; however, the reaction rates for the epoxy blends were found to be higher than that of the neat epoxy. To understand the interrelationship between the cure kinetics and the morphological structure of the epoxy blends, the morphology evolution as a function of extent of cure was examined using scanning electron microscopy (SEM). The higher reaction rate observed in the epoxy blends is proposed to be caused by enhanced molecular mobility as a result of plasticization of the crosslinking epoxy networks by the PEI. In addition, phase separation of the epoxy-PEI blends during cure induced an uneven segregation of the epoxy and amine in different domains. These factors which affected the cure kinetics were discussed. The proposed kinetic model has been found to describe well the cure behaviour of the epoxy-PEI blends up to the vitrification point.