The international seminar "Material Behavior and Physical Chemistry in Liquid Metal Systems" was organized by the Institute of Materials and Solid State Research of the Karlsruhe Nuclear Research Center (Karlsruhe, Federal Republic of Germany). The seminar was held at the Nuclear Engineering School of the center on March 24-26, 1981. The aim of the seminar was to give metallurgists, chemists,. and physicists working in different areas of the science and technology of liquid metals an opportunity to discuss the basic work and the need for further work in this field. Since the seminar was held near one of the laboratories which for the last few years has been engaged in liquid alkali metal studies, partic­ ipants also had an opportunity to observe modern equipment for liquid alkali metal research. Interest in the application of liquid metals as working fluids in energy production, conversion, and storage is increasing. The technology has already demonstrated its high standards, which make possible the operation of large sodium-cooled fast reactors. Past conferences have shown, however, that there is still a lack of basic knowledge and understanding. Therefore, the aim of the present seminar was to discuss basic work in detail, and most of the papers contributed to this objective.