This volume contains the papers presented at the 5th International Conference on Object-Oriented Information Systems, OOIS '98, held at the University de La Sorbonne, Paris, France, 9-11 September 1998. The papers outline research in object-oriented concepts and principles, object-oriented methods and tools, as well as reports on industrial projects from both researchers and practitioners in the field. The conference especially highlighted areas of significant interest to industry, which provide innovative directions for the development of next generation systems such as: coping with legacy systems; transition to object technology; lessons learned from large scale projects using objects; and object relational design.