Gillette (USA), C.D. Klaassen (USA), J.J. Kocsis, (USA), D.B. Menzel (USA), M. Mercier (Belgium), R.A. Neal (USA), F. Oesch (BRD), S. Orrenius (Sweden), H. Remmer (BRD), M. Roberfroid (Belgium), H. Vainio (Finland) and C.M. Witmer (USA), acting 'as a committee under G.G. Gibson (UK), D.J. Jollow (USA), D.V. Parke (UK) and R. Snyder (USA), co-chairmen, THE SECOND INTERNATIONAL SYMPOSIUM ON BIOLOGICAL REACTIVE INTERMEDIATES was convened at the University of Surrey in the United Kingdom on July 14-17, 1980. This volume derives directly from the presentations at the symposium. The University of Surrey, which is located in Guildford, Surrey, provided a congenial atmosphere for this conference and we would like to take this opportunity to thank the local organizing committee and especially Dr. G. Gordon Gibson, for all their efforts in both scientific and social arrangements. Special thanks are extended also to the graduate students of the Biochemistry Department (especially Ms. Tricia Breacker and Mr. Paul Tamburini) and to the conference secretaries who unstintingly gave of their time in a variety of roles to ensure the smooth functioning of the symposium. We wish to acknowledge the tireless efforts of the distinguished scientists who agreed to chair the sessions of the symposium: A. Hildebrandt (BRD), H. Remmer (BRD), L. Goldberg (USA), S. Orrenius (Sweden), H. Uehleke (BRD), J.R. Gillette (USA), C. Netter (BRD), M. Mercier (Belgium), F. Oesch (BRD), E. Boyland (UK), J.E. Gibson (USA), C.D. Klaassen (USA) and J.W. Gorrod (UK). The mounting of a large scale international symposium is fraught with many impediments, not the least of which are the financial and logistical problems of assembling a group of internationally distinguished scientists in one place at the same time. Success in such endeavors requires concerned and active sponsors. The three sponsoring