A miscible PMMA/PC blend was prepared by a rapid casting method, and its miscibility was confirmed by d.s.c. The specific heat capacity of the two-phase blend (5/5) was larger than that of the one-phase blend. The thermal diffusivity and the conductivity of the blend (5/5) slightly decreased with the increase of temperature up to 450-460 K (LCST), and then decreased abruptly with increasing of temperature. The thermal diffusivity at solid state was always smaller than the one estimated by the linear relation with PC content, while in liquid state it always changed linearly with PC content. On the other hand, the experimental thermal conductivity in the liquid state was always smaller than the value estimated by the linear relationship with PC content, while in the solid state it changed linearly. Finally, we discussed adaptability of prediction equations appearing in literature to the conductivity. The Filippov, NEL and power law equations were found to describe adequately the thermal conductivities of PC/PMMA blends in liquid and solid states.