Advances in molecular biology have enabled leaps forward in the determination of virus phylogenetic history. This detailed 1995 book results from the invitation to foremost experts to give essays on aspects of virus biology. Initial chapters cover impacts of viruses and their control. Further chapters detail genetic variation of viruses and the molecular basis of interrelations with hosts. This leads to discussions of interactions with the host at the population level, and their molecular basis and evolution. Seventeen chapters follow, by specialists on particular groups of viruses describing their impact, genetic origins, sources of variation, population genetics and interactions with hosts. Practical virologists will find the chapters on phylogenetic analysis techniques very useful. The adaptive nature of viruses makes this work highly relevant to evolutionists.