This book contains thoroughly revised versions of the papers presented at the 1994 Ch?tillon Spring School held in May 1994. This spring school was the 22nd event in a series of advanced seminars presenting important new areas of research to the theoretical computer science community. The interdisciplinary area of constraint (logic) programming and constraint-based systems has recently developed a discernible identity, which is promising both in terms of simple and general foundations and in terms of significant practical applications. The 15 papers presented in this volume make the new area accessible to all interested computer scientists and report the state of the art in this exciting new field, particularly in the subfield of constraint logic programming.