Abstract: The social differentiation in small groups of captive female hamadryas baboons was examined. Two positions could be distinguished: The highest ranking female, denoted as central individual, monopolized nearly all the presenting, mounting and grooming interactions. The lower ranking females, denoted as peripheral individuals, competed for access to the central female. All dyads of a group were arranged in a rank order according to the amount of sociopositive interaction which they reached within the group. This order of prevalence of dyads was positively correlated with the sum of dominance ranks of the dyad and the mutual attraction as estimated by choice tests. A multiple rank correlation demonstrated that the influence of the sum of ranks and of mutual attraction were nearly independent. If an individual's relationship to the central female had a higher rank of prevalence than that of its rival, it intervened more often and more successfully when the rival tried to interact with the central female. Interventions served to defend rather than to establish relationships. The results are compared with other studies that discuss basic principles governing structuring processes in nonhuman primate groups.