This book contains 55 chapters that summarize referred to the special issue of Drug Development lectures given during the Fifth International Research (Volume 31, Number 4, April 1994). Symposium on Adenosine and Adenine Measured by the number and quality of presenta- Nucleotides held in Philadelphia, Pennsylvania, tions, and by the record number of participants, U. S. A. , May 9-13, 1994. The symposium and the Fifth International Symposium on Adenosine its proceedings follow four previous symposia and Adenine Nucleotides was clearly an intel- and their published proceedings. Previous sym- lectually stimulating meeting. It is safe to posia were held in Banfff, Canada (1978), conclude that the purine research field is vibrant Charlottesville, Virginia (1982), Munich, and still growing. Adenosine has rapidly become Germany (1986), and Lake Yamanaka, Japan the drug of choice for the acute management (1990). of supraventricular tachyarrhythmias and was The program included a wide range of sub- recently approved for use in combination with jects from molecular and cellular biology to cardiac imaging for detection of ischemic heart clinical applications. Great emphasis was placed disease. Additional clinical applications of on cutting edge information derived from studies adenosine and adenosine-related drugs and ATP using molecular and cellular biology techniques seem closer than ever before. The editors would like to express their grati- applied to the field of adenosine and adenine nucleotide research. Likewise, the program tude to the distinguished contributors for their included a number of presentations on poten- excellent chapters and to all participants.