Vaporization is an important property in materials research since it limits the use of the materials at high temperatures and since valuable thermodynamic data can be determined from vapour pressures. High-temperature mass spectrometry is the most versatile method for the elucidation of vaporization processes. Numerous results have been obtained. This article describes the fundamentals of the method and gives examples of its application. These examples describe the determination of thermodynamic properties for the gaseous species and condensed phases. The materials considered are salts, alloys and graphitic materials. They are of interest for metal halide lamps, superalloys, and nuclear reactors.