The present volume is the first of a projected four-volume treatise. This volume contains the following chapters: "Synthesis and Reaction of Pyrimidine Nucleosides," "Synthesis and Properties of Purine Nucleosides and Nucleotides," and "Synthesis and Properties of Oligonucleotides." These three chapters were selected for inclusion in Volume I because the areas have provided the basis and impetus for the initiation and development of the other areas of research, which will be described in subsequent volumes. Each chapter is rather comprehensive in nature and should provide a ready reference source for not only the novice but also the experienced investigator or researcher. The chapters have been prepared by authors with considerable experience in each particular area of research, and this has resulted in a lucid presentation of each well-defined area. These volumes were designed with medicinal chemists, medicinal organic chemists, organic chemists, carbohydrate chemists, physical chemists, and biological chemists in mind. However, because of the tremendous recent interest in this research area owing to the biological and chemotherapeutic evaluation of nucleosides and nucleotides as anticancer, antiviral, and antiparasitic agents, these volumes should also be valuable additions to the libraries of virologists, biochemical pharmacologists, oncologists, and pharmacologists. We would like to thank the authors for their enthusiasm and help in making these volumes available to the scientific community.