By their powers of reason scientists will be able to extract from nature the answers to their questions. From: Critique of Pure Reason, 1781 Immanuel Kant (1724-1804), German Philosopher History is a composite of stories. The history of the biological disciplines has been written by all those who opened the gates of new knowledge by generating ideas and the experiments to support them. Previous authors have attempted various approaches to the history of virology, as is reflected in the numerous books and book-series issuing from the publishing houses. This volume is an attempt at a compre hensive yet compact survey of virology, which has meant penetrating the rigid limits of the separate disciplines of biology in which virologists have worked. Writing this history of experimental virology was really a search for the origins and for vital signposts to portray the wide scope of the knowledge attained thus far. This was done in com plete awareness of the fact that every presentation depends heavily upon the perspective of the observer, and of necessity communi cates only a part of the whole. The present scientific story hopes to recount the most important knowledge achieved during this past century - the first century of the exciting developments in virology.