In the summer of 1984, both of us were working with Professor Yechiel Becker in the Laboratory for Molecular Virology at the Hebrew University-Hadassah Medical center in Jerusalem. During a discussion about the increasing number of specialized journals and monographs, Dr. Becker pointed out that none covered both the clinical and molecular aspects of neurotropic virus infections, and he urged us to develop such a book with the help of colleagues who were conducting highly-regarded research in their individual areas related to neurotropic viruses. The responses to our request were gratifying, and each contribution provided both a comprehensive clinical description of the neurologic disease produced by a specific virus and an up-to-date review of the current research in the pathogenesis of the disease, with particular attention given to molecular mechanisms. Most, but not all chapters were written by clinical neurologists who applied basic science strategies and methodologies to the question of how neurotropic viruses produce disease. other chapters were written by virologists known for their longstanding commitment and expertise in the analysis of the pathogenesis of neurotropic virus infections. Thus, this unique monograph should be valuable to all clinicians caring for patients with CNS viral diseases and to "neurovirologists" needing an update of the clinical and molecular pathogenesis of neurotropic virus infections. While this monograph was being prepared, a rapidly expanding literature indicated that the human lenteviruses, human immunodeficiency viruses (HIV) and HTLV-1 were highly neurotropic.