This book constitutes the refereed proceedings of the First International Conference on Fundamental Approaches to Software Engineering, FASE'98, held as part of the Joint European Conferences on Theory and Practice of Software, ETAPS'98, held in Lisbon, Portugal, in March/April 1998. Besides two invited presentations and three system demonstrations, this volume presents 18 revised full papers selected from a total of 59 submissions. Among the various fundamental software engineering issues addressed are formal methods, specification languages, refinement, object-oriented modeling, software architectures, statecharts, model checking, etc.