These volumes record the presentations made at the VIII International Symposium on Purine and Pyrimidine Metabolism in Manheld at Indiana University, Bloomington, USA from May 22- May 27, 1994. This was a continuation of meetings held every three years with the idea of bringing clinicians and basic scientists together, which we hope results in cross-fertilization of ideas. Some of the papers presented in this volume represent oral contributions and others are from posters, but we emphasize that both are considered of equal merit. As is obvious from a perusal of the titles of the papers there has been a shift in the focus of this meeting, which reflects a general shift in the area of purine and pyrimidine metabolism. The emphasis has definitely shifted to gene structure and molecular genetics, with the beginnings we hope of gene therapy as an important branch of this area of science. Although many of the inherited diseases discussed in this text can be treated with drugs, the major thrust in the futurewill be in gene therapy, where the gene (or cDNA) will be used to treat the patient with enzyme deficiency, particularly if the patient is young. As can be seen from the Iist of authors there is a remarkable degree of international cooperation in this area across countries and continents. We thank the many participants who have attended these symposia many times, and we welcome the large group of scientists from Eastern Europe who are attending this meeting for the first time.