Addition of allylic and epoxy monomers as reactive plasticizers in polyetherimide(PEl) was investigated to improve processibility without reduction of thermo-mechanical properties of the PEI. Blends of various concentrations of PEI and monomers with different initiators/curatives were prepared by solvent and melt blending methods. Miscibility study indicated that unpolymerized blends of PEI with either allylic or epoxy monomers were miscible with PEI at more (than 40%PEl but partially immiscible at low PEI content. Curing characterization showed that peroxides and aromatic amine capable of initiating cure at high temperatures thus considered as suitable initiator/curative. Thermal properties study indicated that all compositions phase separated when polymerized but retaining thermomechanical properties of the PEI with only slight reduction of glass transition temperature.