This volume contains the proceedings of the third in a series of biennial NEC Symposia on Fundamental Approaches to New Material Phases sponsored by the NEC Corporation, Tokyo, Japan. The symposium was held from October 7 to 11, 1990, at the Hakone Kanko H9tel in Hakone. About 40 invited participants stayed together, became involved in intense discussions, and freely exchanged ideas both in and out of the conference room, which faced Mt. Fuji, the beautiful lake Ashinoko, and the quiet landscape in the old crater. The title of this volume, Ordering at Surfaces and Interfaces, which was also the title of the third symposium, describes the aim of the symposium: to discuss ordering properties and their underlying mechanisms at surfaces and interfaces. The topics treated include the reconstruction of surfaces of semiconductors and metals, atomic and magnetic ordering at interfaces, theoretical tools to study or dering mechanisms at surfaces and interfaces, ordering in adsorbate-surface sys tems, such as alkali-adsorbed silicon surfaces, electric current effects on semicon ductor surfaces and many related STM (scanning tunneling microscopy) results.