Solid source mass spectrometry is increasingly widely being used for impurity analysis in materials research. Special advantages are its high sensitivity (1 part in 10⁹), approximate equality of sensitivity for all elements, simplicity of interpretation, overall coverage of the elements in a single analysis and ease of adaptation to new problems. A brief description of the type of mass spectrometer required for such analysis is given and the basic features of the spectra obtained using spark and arc type ion sources are discussed. The method of making an analysis is described in detail and examples are given of applications and results in metallurgy, solid state physics, reactor technology and inorganic chemistry.