The macroscopic homogeneity of a series of two-component epoxy networks (EN) is indicated by a single glass transition temperature as measured by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). However, the heterogeneity at the nano-scopic length scale of the order of chain persistence length p exists as indicated by a broadening of T, intervals. With the assumption of this nano-scopic heterogeneity, the composition dependence of the heat conductivity of EN in a broad temperature range was quantitatively analyzed by a step-by-step averaging (SSA) approach. (C) 2004 Elsevier B.V. All rights reserved.