This volume on enzootic bovine leukosis (EBL) and bovine leukemia virus (BLV) is the second in our series Developments in Veterinary Virology. Each book in this series is devoted to a major virus disease of agricultural significance. The chapters in each volume are planned to supply information on a range of subjects from pathogenesis of the causative virus to vaccination, eradication, and rules regarding disease control. The present volume on enzootic bovine leukosis and bovine leukemia virus updates the reader on the disease and its causative agent and includes the nucleotide sequence of the BLV genome as well as data on its integration into the DNA of the tumor cell. Insights into diagnosis, veterinary legislation, and the economic aspects of EBL are also provided. Intense research conducted on EBL and BLV during the course of a decade is presented in a most concise and in-depth manner, so as to provide the reader with a comprehensive overview of this economically important disease of cattle. I wish to thank the editors, A. Burny and M. Mammerickx, as well as all the authors, for making this excellent book available at a stage when the knowledge on bovine leukemia virus will also contribute to our understanding of the virus causing human AIDS.