This book contains the proceedings of the international workshop on Many-Atom Interactions in Solids, which was held June 5-9, 1989, in Pajulahti, Finland. The purpose of the workshop was to bring together physicists, chemists and materials scientists working in the field of interatomic interactions and their applications in computer simulations of condensed matter. The workshop attracted a good fraction of the active groups in the field, and created lively discussion and interchange of ideas. The contributions in this volume have been grouped by the editors into review type articles and more specific applications to different topics. The order of the articles does not follow the order of the presentations in the workshop. The editors wish to express their gratitude first of all to all the workshop par ticipants for creating an enjoyable and fruitful workshop and to the contributors for their efforts in putting together these proceedings. We hope that this volume will be a useful resource for practitioners in and newcomers to this exciting field. We would like to thank Jens N!l1rskov for his help in planning the scientific pro gramme and Eija Jarvinen for taking care of most of the practical arrangements of the workshop. The workshop was made possible by financial support from the Finnish Ministry of Education, the Research Institute for Theoretical Physics (Helsinki), NORDITA (Copenhagen), and Helsinki University of Technology.