What is high dimensional probability? Under this broad term one finds a collection of topics associated by the fact that ñ plays a key role in each, whether the idea of high dimension ñ is expressed in the problem or in the methods by which it is approached. For example, the study of probability in Banach spaces gave impetus to a number of methods whose importance has gone far beyond the original goal of extending limit laws to the vector valued case. Familiar applications are in the areas of empirical processes, the use of majorizing measures to study regularity of stochastic processes, and the theory of concentration of measure. Many of the new ideas, results and directions of this newly evolving field were explored on a broad front at the Conference on High Dimensional Probability held at Oberwolfach in August 1996. The papers in this volume are marked by vitality and diversity and will give researchers and graduate students in probability or statistics much to whet their interest.