Much of organic chemistry is based on the ability of suitably structured chemicals to bind together through the formation of covalent bonds. Biochemistry is replete with exam ples of enzymatically catalyzed reactions in which normal body constituents can be linked through covalent bonds during the process of intermediary metabolism. The finding that xenobiotic chemicals that enter the body from the environment, are metabolized to highly reactive species, and then covalently react with cellular macromolecules to induce toxic and carcinogenic effects was an observation that spawned the research featured in the Fifth International Symposium on Biological Reactive Intermediates (BRI V). The group of investigators that became fascinated with this process and its signifi cance in terms of human health began their discussions in Turku, Finland (J 975), and continued them at Guildford, England (1980), College Park, Maryland (1985), Tucson, Arizona (1990), and Munich, Germany (1995). Among the results were a series of reports listed below, as well as the book for which this serves as the Preface. * Jollow, DJ., Kocsis, J.J., Snyder, R. and Vainio, H. (eds), Biological Reactive Intermediates: Formation, Toxicity and Inactivation, Plenum Press, NY, 1975. * Snyder, R., Park, D.V., Kocsis, J.J., Jollow, D.V., Gibson, G.G. and Witmer, C.M. (eds), Biological Reactive Intermediates II: Chemical Mechanisms and Biological Effects, Plenum Press, N.Y., 1982.

Historically we have separated the disciplines of Chemistry and Biochemistry by recognizing that the distinguishing characteristic of Biochemistry is the catalysis of reactions by enzymes. Enzymes permit metabolic reactions which would otherwise require extremes of temperature, pressure or pH, often associated with Chemistry, to proceed under ambient conditions of the body. Under some conditions chemical reactions occur in vivo in which products of enzymatic reactions proceed to undergo further reactions non- enzymatically with cellular macromolecules. The results can often be seen as toxic or carcinogenic responses. The chemicals that initiate these reactions are termed "biological reactive intermediates. " The International Symposia on Biological Reactive Intermediates (BRI) began in 1975 at the University of Turku, Finland and have since convened at the University of Surrey, Guildford, The United Kingdom (1980), the University of Maryland, College Park, Maryland (1985), the University of Arizona, Tucson, Arizona (1990), the GSF Forschungszentrum and Technical University of Munich (1995) and, most recently, at the Universite Rene Descartes, Paris, France (2000). The Symposium was organized by an International Planning Committee co-chaired by P. Dansette (Paris, France) and TJ. Monks (Austin, Texas). The committee included: P. H. Beaune (Paris, France), M. De\aforge (Saclay, France), G. P. Gervasi (Pisa, Italy), G. G. Gibson (Guildford, UK), H. Greim (Munich, Germany), DJ. Jollow (Charleston, South Carolina), P. Moldeus (Sodertalje, Sweden), I. G. Sipes (Tucson, Arizona), R. Snyder PJ. van Bladderen (Zeist, The Netherlands). They were (Piscataway, New Jersey), and assisted by an International Scientific Program Advisory Committee which included: TJ.

Much of organic chemistry is based on the ability of suitably structured chemicals to bind together through the formation of covalent bonds. Biochemistry is replete with exam ples of enzymatically catalyzed reactions in which normal body constituents can be linked through covalent bonds during the process of intermediary metabolism. The finding that xenobiotic chemicals that enter the body from the environment, are metabolized to highly reactive species, and then covalently react with cellular macromolecules to induce toxic and carcinogenic effects was an observation that spawned the research featured in the Fifth International Symposium on Biological Reactive Intermediates (BRI V). The group of investigators that became fascinated with this process and its signifi cance in terms of human health began their discussions in Turku, Finland (J 975), and continued them at Guildford, England (1980), College Park, Maryland (1985), Tucson, Arizona (1990), and Munich, Germany (1995). Among the results were a series of reports listed below, as well as the book for which this serves as the Preface. * Jollow, DJ., Kocsis, J.J., Snyder, R. and Vainio, H. (eds), Biological Reactive Intermediates: Formation, Toxicity and Inactivation, Plenum Press, NY, 1975. * Snyder, R., Park, D.V., Kocsis, J.J., Jollow, D.V., Gibson, G.G. and Witmer, C.M. (eds), Biological Reactive Intermediates II: Chemical Mechanisms and Biological Effects, Plenum Press, N.Y., 1982.

Historically we have separated the disciplines of Chemistry and Biochemistry by recognizing that the distinguishing characteristic of Biochemistry is the catalysis of reactions by enzymes. Enzymes permit metabolic reactions which would otherwise require extremes of temperature, pressure or pH, often associated with Chemistry, to proceed under ambient conditions of the body. Under some conditions chemical reactions occur in vivo in which products of enzymatic reactions proceed to undergo further reactions non- enzymatically with cellular macromolecules. The results can often be seen as toxic or carcinogenic responses. The chemicals that initiate these reactions are termed "biological reactive intermediates. " The International Symposia on Biological Reactive Intermediates (BRI) began in 1975 at the University of Turku, Finland and have since convened at the University of Surrey, Guildford, The United Kingdom (1980), the University of Maryland, College Park, Maryland (1985), the University of Arizona, Tucson, Arizona (1990), the GSF Forschungszentrum and Technical University of Munich (1995) and, most recently, at the Universite Rene Descartes, Paris, France (2000). The Symposium was organized by an International Planning Committee co-chaired by P. Dansette (Paris, France) and TJ. Monks (Austin, Texas). The committee included: P. H. Beaune (Paris, France), M. De\aforge (Saclay, France), G. P. Gervasi (Pisa, Italy), G. G. Gibson (Guildford, UK), H. Greim (Munich, Germany), DJ. Jollow (Charleston, South Carolina), P. Moldeus (Sodertalje, Sweden), I. G. Sipes (Tucson, Arizona), R. Snyder PJ. van Bladderen (Zeist, The Netherlands). They were (Piscataway, New Jersey), and assisted by an International Scientific Program Advisory Committee which included: TJ.