This book describes a wide variety of speculations by many authors about the consequences for humanity of coming into contact with extraterrestrial intelligence. The assumptions underlying those speculations are examined, and some conclusions are drawn. The book emphasizes the consequences of contact rather than the search, and takes account of popular views, not just those of scientists. As necessary background, the book also includes brief summaries of the history of thinking about extraterrestrial intelligence, searches for life and for signals, contrasting paradigms of how contact might take place, and the paradox that those paradigms allegedly create. Michael Michaud has been actively engaged in discussions of these issues within the International Academy of Astronautics. He served as Director of the U.S. State Department's Office of Advanced Technology and as Counselor for Science, Technology, and Environment at the American embassies in Paris and Tokyo.