It is argued that numerous issues directly relevant to the field of personality and social psychology are present and may become increasingly important in the U.S. space program. It is further suggested that data from personality and social psychology have been underused resources in the U.S. space program. The responsibility for this outcome is seen as resting both with investigators and in structural aspects of NASA. The contrasting centrality of psychology in the Russian space program is noted. Finally, suggestions for increasing the role of personality and social psychology in the U.S. space program are offered.The space program confronts one of the last frontiers in exploration and as such provides great challenges for the application of psychological principles and the refinement of social psychological theories. At our present stage of spaceflight, crews leave the earth in a fragile vehicle to face a hostile and unforgiving environment in which weightlessness and "space sickness" are givens. The ability of individuals to adjust to extreme crowding and discomfort, to postpone gratification during years of rigorous training, and to perform at a high level is a tribute to human adaptability.Relatively few psychological problems among crew members have manifested themselves in our two decades of spaceflight. However, a conceptual analysis of the likely course of future missions suggests that more rather than fewer psychological issues may arise as we turn to the exploitation of space. Certainly, common factors in the foreseeable future will continue to be danger, isolation, relative crowding, and limited access and escape. In other words, spacecraft will continue to be potentially volatile microcosms.I have argued elsewhere (e.g., Helmreich, Wilhelm, & Runge, 1980;Radloff & Helmreich, 1968) that part of the success of the space program can be attributed to the fact that although the psychological and physical costs of spaceflight are high (in danger and discomfort), the tangible and intangible rewards have also been great in terms of public adulation and even financial and political benefits. In terms April 1983 • American Psychologist