The thermoelectric power of metals and alloys is a relatively easily measured physical property that has become increasingly valuable in recent years for the information it can yield on electron and phonon transport processes. It is a particularly sensitive property for investigating dilute alloys, the effect of transition metal impurities in metals, and magnetic ordering. Links with other transport properties are provided by the use of the Wiedemann-Franz law and the Matthiesson rule in the basic theory. This review covers recent developments in the use of thermoelectric power as a research tool.