Meet the animal stars of space, some celebrities and some unsung, who have been man's vanguard stand-ins in the exploration of space. The authors, both Majors in the United States Air Force, describe the events in which animals have figured, and by the way provide a view of the ever-widening circle of experiment. The United States has used mice, monkeys, chimpanzees, the latter very satisfactory because they most closely resemble man and can be tested for psychological as well as physiological functioning (problem-solving in space); the Russians prefer dogs, perhaps because of Pavlovian experience. The part of Colonel John Paul Stapp of the Aeromedical Field Laboratory, of the U.S. Air Force Medical Corps with seventeen veterinarians assigned to the Air Research and Development Command, of the Vivarium at Holloman Air Force Base in training and preparation is all described. The authors transmit the excitement of the countdown, tracing with particular interest in detail the first test of reaction in actual spatial flight with Enos at the helm on Nov. 29, 1961. The more recent programs include a fourteen-day test of responses under space conditions. There is an excellent glossary of space terms, and the total book is a satisfactory introduction, for young adults in particular, to space research.