As a model system for a thermoplastic/thermosetting composite material, a stoichiometric amine-epoxy formulation was cured in the presence of the thermoplastic poly( vinylpyrrolidone) (PVP). The epoxy system consisted of the resin diglycidyl ether of bisphenol A ( DGEBA) and the aromatic curing agent 4,4'-diaminodiphenylsulfone (DDS). Using nanoindentation, profiles of the sample Young's modulus, E(s), the hardness, H, as well as the plasticity index, psi, were measured and found to show significant variations. From the hardness profile three different interphase (IP) zones can be identified. They add up to a total interphase width of similar to 230 microns. Further information on the nature of the interphasial zones was deduced from temperature-dependent dynamic mechanical thermal analysis ( DMTA) and energy-dispersive analysis of X-rays (EDX). In particular, the outer edge of zone Z2 is consistent with the width of the amine depletion zone. Finally, the different IP zones are discussed in terms of the diffusion processes taking place during the epoxy curing procedure.