The structure of grooming relations was studied in three captive groups of stumptail macaques, two heterosexual (consisting mainly of females) and one all male. Compared to the heterosexual groups, social hierarchy in the all-male group was less linear, and agonistic and peaceful activity of low-ranking individuals toward high-ranking ones was higher. In addition, in the all-male group received grooming was more variable than performed grooming and showed stronger dependence on age. No effect of maternal kinship was found in the all-male group, and individual preferences were also less marked in this group than in heterosexual groups. These differences tend to be related to dominance style and dispersal patterns. (C) 1996 Wiley-Liss, Inc.