Guest Editors' Preface

This special issue of the Journal of Complexity contains six articles corresponding to some of the talks delivered at the third conference of the Foundations of Computational Mathematics (FoCM) in the workshop on information-based complexity. This workshop, one of 14 FoCM workshops, was held at Oxford University July 26 28, 1999. For more information about FoCM conferences (in the past and in the future) consult the Web page