These papers are the proceedings of the International Symposium on the Chemistry and Biology of Pteridines and Folates. The book brings together contributions from some 250 scientists from chemistry, biochemistry, biology, pharmacology, and medicine to present and discuss recent advances in this expanding field. Pteridines fulfil many roles in nature, ranging from pigments to essential co-factors for numerous redox and carbon transfer reactions. This large diversity of function is unified by the unique chemistry of the pteridine heterocycle. Emphasis in the book is given to: the progress of antifolates in cancer therapy, with emerging new compounds of broad range effectiveness and with gene therapeutic approaches; on the role of folates in nutrition and their pathological changes; and on new findings in pteridine and folate enzymes.