This book is a collection of papers reflecting the conference held in Caracas, Venezuela, in January 1994 in celebration of Professor Mischa Cotlar's eightieth birthday. Presenting an excellent account of recent advances in harmonic analysis and operator theory and their applications, many of the contributors are world leaders in their fields. The range of topics in this volume promotes cross-pollination among the various fields covered. Such variety makes Harmonic Analysis and Operator Theory and inspiration for graduate students interested in this area of study.