This book is the first volume of the proceedings of the Canadian Mathematical Society Annual Seminar on Mathematical Quantum Theory, held in Vancouver in August 1993. The seminar was run as a research-level summer school concentrating on two related areas of contemporary mathematical physics. The subject of the first session, quantum field theory and many-body theory, is covered in the present volume; papers from the second session, on Schr odinger operators, are in Volume 2. Each session featured a series of minicourses, consisting of approximately four one-hour lectures, designed to introduce students to current research in a particular area. In addition, about thirty speakers gave one-hour expository lectures. With contributions by some of the top experts in the field, this book provides an overview of the state of the art in mathematical quantum field and many-body theory.