[en] Following a brief history of thermoelectricity and an introduction to its basic theory this paper reviews the present position concerning generation of electricity by the thermoelectric effect and considers future prospects. Factors that influence the selection of materials for a particular application are discussed, together with the preparation and properties of established materials. A section dealing with the fabrication of thermo-elements and the various configurations employed in module construction is followed by a general discussion of thermoelectric generators. Applications of radioisotopic thermoelectric generators in space research, for submerged situations and in the medical field are discussed and illustrated. (U.K.)