An intensive study during 3 months shows that polyspecific associations of Cercopithecines sometimes may be very stable, conducing to a total common exploitation of the environment. In spite of some differences in vertical stratification and diet of associated species, it appears that the association is based on a large overlapping of ecological needs. Association remains thanks to obvious behavioral affinity between the species and to supraspecific social organization where one species is ‘leader’. Life in association allows a better quantitative and qualitative exploitation of the milieu.