It was observed the effects of captivity on the reproductive competence of monkeys, to measure the degree of adaptation to a confined situation. These observation were made on Cebus, Aotus, and Saimiri monkeys, from two different monkeys colonies, facing a project of establishment a breeding monkey colony at the IICS. It was observed the behavior of the monkeys concerning the aggressivness against the other monkeys in the cage and themselves, the organization of social groups, and its hierarchy. It was evidenced the importance of the tryning of the staff dealing with the monkeys, as factor influencing the behavior of the animals. It was observed the importance of the organization of the colony, concerning the surroundings of the cages, ventilation, room temperature, illumination, presence of personnel, location of other cages, as factors exerting a strong influence in the behavior of the monkeys