The degree to which cooperative behavior is kin-correlated in different primate species is reviewed. The mechanisms whereby individuals might recognize related conspecifics are also considered. Different mating systems, in conjunction with dispersal behavior, are hypothesized to produce particular patterns of kin association in primate groups. These patterns determine what classes of kin are likely to be distinguished, as well as which mechanisms of recognition would be predicted. Association or familiarity during development is concluded to be the most important mechanism of kin discrimination in the primates.