Many groups of biologically important compounds experience cycles of furious research activity and near oblivion. The purines however seem not to be falling into such a pattern. Interest seems to be continuing almost exponentially with no sign of diminution. The result is a frighteningly extensive literature and an increas- ing demand for international conferences and symposia. Unfortunately meetings such as these also spawn increasingly voluminous proceedings and it becomes more and more difficult for a newcomer to the area, or a non- specialist, to obtain the general introductory survey he needs. This volume therefore is not intended to be comprehensive - far from it. We have tried to be selective in the material presented and the references quoted. They should provide a quick guide and access to key works in the literature which can be expanded by library or computerised searching. We hope that our efforts will widen the appreciation of purines as biologically important substances and will herald the day when more purine related drugs than the handful currently available are used for the selective treatment of disease. We are grateful to the many authors and publishers who have given permission to reproduce figures or quote unpublished results, and to Anne Stone for her patient typing of the manuscript.