Volume 251 of the series Contemporary Mathematics published by the American Mathematical society contains the refereed proceedings of a conference, held at Temple University in Philadelphia in 1998, entitled Analysis, Geometry, Number Theory: The Mathematics of Leon Ehrenpreis. The conference was supported, in part, by the National Science Foundation and by Temple University. I served as Editor of this volume together with the following colleagues: S. Berhanu, M. Knopp, G. Mendoza, and E.T. Quinto.