th th This volume comprizes articles presented at the joint IX International and 6 Euro pean Symposium on Purine and Pyrimidine Metabolism in Man held in Gmunden, Austria, June 1 through 7, 1997. Since the first of this series of meetings was held in Israel in 1973, conventions were organized every three years in different parts of the world including the USA, Japan, and Europe. The different aspects of purine and pyrimidine metabolism bring together re searchers working in molecular genetics, biochemical pharmacology, biochemistry, devel opmental biology, immunology, epidemiology and the clinics. Oriented research in the field has been seminal for the development of potent anticancer and antiviral drugs. As the number of genes which are cloned, grows, the understanding of metabolism is increas ingly enlarged and might provide leads to further improve therapeutic concepts and to bet ter understand mechanisms responsible for the development of resistance against these drugs. In certain diseases purine and pyrimidine analogs represent not only the drugs of choice but in fact are the sole therapeutic alternative at present. The field has also taken an early lead in attempting to correct inborn errors of purine and pyrimidine metabolism by gene therapy. The organization of this meeting involved a large number of people who dedicated their time in an effort to make this symposium a success. We thank the Abstract Review Committee, the International Advisory Board and in particular the Symposium Secretariat for doing a wonderful job.