This book should be of value to all those who are considering the use of or have only just begun to use the computer as a learning aid, regardless of the educational level and the discipline being considered. Although the focus is on computer-based instruction in physics and mathematics at the university- and secondary-school levels, the strategies and problems are universally applicable. At the NATO Advanced Study Institute upon which this volume is based, the obstacles encountered by those engaged in such activities were similar in each of the eighteen countries represented. Despite many false starts by those engaged in applying the computer as a learning aid, we believe unequivocally that the computer presents a unique educational tool yet to be exploited adequately. The reasons for slow development may become obvious as one reads this book: the effort required to achieve measurable success is not trivial. Extensive planning and team efforts are often necessary. Unfortunately, many well-intentioned educators discover this too late. We emphasize very early that it is the opportunity to engage students as active participants in the learning process which sets computer-based learning apart from the learning potential of other electronic media.