This volume presents a discussion of the biological effects produced following the metabolism of xenobiotic chemicals to chemically reactive metabolites, i.e., toxic and carcinogenic effects, which have been the basis of all five earlier volumes in this series. In particular, this volume devotes sections to structure-activity relationships, recent advances in the understanding of the chemistry of reactive metabolites, and the generation and activity of reactive oxygen species with special emphasis on nitric oxide. There are also segments on DNA damage by reactive metabolites and DNA repair, tissue specific responses to BRIs, and human health effects of BRIs. The papers that comprise this volume were submitted by world class scientists who were in attendance at The Symposium on Biological Reactive Intermediates VI at the Université René Descartes, July 16-20, 2000.