This article describes and recommends various methods for calibration of thermal conductivity vacuum gauges in the pressure range of the order of 10(-1) Pa ( 10(-3) Torr) to an atmosphere and is one of a series published by the American Vacuum Society. It contains data from many sources and represents the opinions of a number of experts in the field. The text was developed by a sub-committee of the Recommended Practice Committee of the American Vacuum Society. The Thermal Conductivity Gauging Committee is made up of users and manufacturers of vacuum gauges who have a variety of experience in the practical use of thermal conductivity gauges.