Thermal conductivity, thermal diffusivity and specific heat, namely the thermal properties, are the three most important physical properties of a material that are needed for heat transfer calculations. Recently, polymer has become an outstanding material in replacing metals and ceramics components. In many industrial applications polymeric materials are composed of a mixture of one or more solid phases. The thermal conductivity of the composed material depends on the arrangement and amounts of each present phase, as well as, on the individual conductivity of each phase. In this work two different phase distributions are studied: the parallel-slab arrangement, and that one having a continuous major phase with a minor amount of a discontinuous second phase. The thermal conductivities are obtained by using two different experimental techniques: the modified split column steady-state method, and the flash thermal diffusivity technique, a non-steady state method. The experimental results obtained are checked against those ones predicted by two theoretical models found in the literature. Key words: thermal conductivity, multiphase systems, polymers.