Here we examine the effects of maternal kinship, reciprocity, and dominance rank on the social relationships of female baboons (Papio cynocephalus ursinus) in a well-habituated, free-ranging group in the Okavango Delta of Botswana. These data are useful for testing comparative hypotheses about the ecological and demographic factors that shape the evolution of social organization in primates and other animals. In this group, adult females had well-differentiated grooming relationships with one another, and limited their grooming to a relatively small subset of available partners. Although there were 19 adult females in the group, the average female groomed only 8 other females, and devoted at least 5% of her grooming to only four other females. Females groomed maternal kin at significantly higher rates and for significantly longer periods than they groomed other females. The bias in favor of maternal kin was not an artifact of a general attraction toward females of adjacent rank. However, members of high-ranking lineages did devote a relatively greater fraction of grooming to maternal kin than members of low-ranking lineages did. Females most often groomed the females from whom they received the most grooming and grooming was very evenly balanced within the majority of dyads. Female rank had little impact upon grooming patterns and there was no evidence that females competed overtly over access to high-ranking partners.