This is the latest supplement to the series "Chemistry of Heterocyclic Compounds" (begun in 1971) which covers the field in its entirety by monographs that reflect the importance and the interrelations of the various compounds, and accommodates the specific interests of the authors. Volume 54 updates the data to provide complete coverage of the heterocyclic chemistry of purines. It contains an exposition of the state of the number of purine derivatives, emphasizing investigations of the nature and reactions of the purine system and suggests possible future trends or developments.