Theoretical calculations of the Seebeck coefficient and electronic thermal conductivity of general materials such as metals, semiconductors, and quantum structures are described, and the dependence of the Seebeck coefficient on doping level and temperature is discussed for lead-salt materials. Experimental Seebeck coefficient was measured for PbS films and the value agreed well with the theoretical value, indicating a high thermoelectric performance comparable to that of PbTe. The temperature dependence of electronic thermal conductivity is also discussed for lead salts. It is shown that minority carriers in the narrow-gap semiconductor significantly affect electronic thermal conductivity, and electronic thermal conductivity at high temperatures can be reduced by high-level doping. (C) 2011 The Japan Society of Applied Physics