Measurements have been made of the thermal conductivity of germanium, silicon, pure (n= 3 × 1016) indium arsenide and impure (n= 1019) indium arsenide. In each case the electronic contributionKeto thermal conductivity has been calculated and the phonon contributionKLestimated by subtraction ofKefrom the experimental values. The thermal resistance of the lattice has not generally been found to be proportional to the absolute temperature as expected for three-phonon processes but the trend is towards a higher power relationship. The lattice resistance of heavily doped indium arsenide has been found to be greater than that of the pure material.