The need for reliable data on thermophysical and thermal optical properties of solid materials grows continually and increasingly. Existing property data, except for selected pure elements and for some simple alloys and compounds, are often not reliable, so in many cases the need for correct and acceptably accurate information can only be met through the measurement of a given property. The measurement-that is, the selection of the measurement method, building or purchase of the apparatus, and the measurement procedure itself­ carries many hidden hazards because methods and their variants are numerous and not appropriate for all materials and temperature ranges, and have many subtle sources of systematic errors, known only to those who have thoroughly studied them. The need for a concise yet complete reference work describing thermo­ physical and thermal optical property measurement techniques, and ultimately, reliable and detailed directions for property measurement discussed at the Sixth European Thermophysical Properties Conference in Dubrovnik, Yugoslavia in 1978, led its International Organizing Committee to launch an international cooperative project with these objectives. This reference work, the Compendium of Thermophysical Property Measurement Methods, is the result of the first phase of work on this program. It is a summary of the state-of-the-art methods for the measurement of thermal and electrical conductivity, thermal diffusivity, specific heat, thermal expansion, and thermal radiative properties of solid materials, from room temperature to very high temperatures.