Recent advances in the field of high pressure techniques influenced me to propose an Advanced Study Institute in Hi0h Pressure Chemistry. It was intended that the summer school should devote itself exclusively to the description and discussion of the effects of pressure in chemistry. Besides typical effects on matter, the application of high pressure techniques to existing research methods were to be treated, as well as pressure effects on reaction rates and equilibria. According to the concept of the Advanced Study Institute Program, the Summer School proceedings were meant to be a high level teaching activity. It was emphasized that the contributions should have the character of surveys rather than of highly specialized reports on recent research results. NOw, following the successful completion of the summer school, which involved very close cooperation with my colleagues during its preparation, it is my sincere wish to thank all the lecturers and contributors to this volume for the extreme care they used in preparing the lectures and manuscripts. I am especially grateful to the members of the organizing committee for their valuable assistance. Finally, the financial support of the Scientific Affairs Division of the North Atlantic Treaty Organization is equally appreciated by participants and organizers of the Advanced Study Institute.