The rheological and thermomechanical properties of some epoxy blends modified with hyperbranched polymers are reported. The effects of different percentages of a multifunctional reactive diluent were investigated to develop formulations that could be processed by RTM (Resin Transfer Molding) and VARTM (Vacuum-Assisted Resin Transfer Molding). The diluent chosen for the study was trimethylolpropane triglycidyl ether, which was added at three percentages: 10%, 20%, and 40%. The hyperbranched modifier used was aliphatic polyester of the fourth pseudo-generation commercialized by Perstorp as Boltorn (TM) H40. A cure cycle composed of a precure at 135 degrees C followed by a postcure at 180 degrees C was adopted. The blends were thoroughly characterized in both the unreacted and cured states. The unreacted blends were characterized by parallel plate rheometry, both in dynamic and isothermal mode. Analysis of the cured samples was carried out through dynamic mechanical tests after precuring and postcuring. The diluent had an impact, due to its peculiar structure, on both the uncured and cured properties. POLYM. ENG. SCI., 49:577-584, 2009. (c) 2009 Society of Plastics Engineers