With concrete plans for long duration flight taking form a new impetus is lent to preparing man for this hostile and unnatural environment. Cramped conditions, isolation from family and loved ones, work stress, fear, and incompatibility with fellow crew, are but a few of the problems suffered by astronauts and cosmonauts during their long missions in orbit about the earth. Although criteria for selection of crew is one aspect of attacking the problem, it has not solved it. Notwithstanding good selection, team combination, and counselling before flight, problems have still occurred with unwanted consequences. Incompatibility of team members, far from being the exception, has been frequent. This has been detrimental both physiologically and psychologically for the individual as well as for the operational success and safety of the missions. Because problems will inevitably occur in future long duration missions, especially when they are of international and multi-cultural nature, the importance of dealing with them is underlined. This paper takes a different approach towards ameliorating these problems, namely that of psychological group training before a mission.