Novel bismaleimide-modified siliconized epoxy intercrosslinked network systems were developed. Siliconized epoxy systems containing 5, 10, and 15% siloxane units were prepared using epoxy resin and hydroxyl-terminated polydimethylsiloxane (HTPDMS) with gamma -aminopropyltriethoxysilane (gamma -APS) as a compatibilizer and dibutyltindilaurate as a catalyst. The siliconized epoxy systems were further modified with 5, 10, and 15% (wt %) of bismaleimide [(N,N ' -bismaleimido-4,4 ' -diphenylmethane) (BMI)I and cured by diaminodiphenylmethane (DDM). Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and heat-distortion temperature measurement of the matrix samples were carried out to assess their thermal behavior. DSC thermograms of the BMI-modified epoxy systems show unimodel reaction exotherms. The glass transition temperature (T,) of the cured BMI-modified epoxy and siliconized epoxy systems increases with increasing BMI content. Thermogravimetric analysis and heat-distortion temperature measurements indicate that the thermal degradation temperature and heat-distortion temperature of the BMI-modified epoxy and siliconized epoxy systems increase with increasing BMI content. The morphology of the BMI-modified siliconized epoxy systems was also studied by scanning electron microscopy (SEM).