A study of social interactions between two adult males and eight adult females throughout sexual cycling, pregnancy, and lactation revealed three types of "long-term" social bond. 1. Persistent, high-frequency bonds. Two male-female dyads exhibited frequent proximity and grooming throughout the study regardless of changes in female reproductive state. In both cases frequent interaction persisted because of preferences which partners showed for each other. Males in both dyads aided their partners when the partners received aggression more often than they aided others. 2. Persistent, low-frequency bonds. Three females showed a preference for the Alpha male over the subordinate male in all reproductive states. Each female appeared to be attempting to establish a "high-frequency" social bond with the Alpha male. However, all were prevented from doing so by two factors: the Alpha male's preference for one female over all others (see above), and competition from this preferred female. Females competed for access to the Alpha male equally often in all reproductive states. 3. Bonds based on "alternating" f emale preference. Three females associated primarily with the subordinate male during lactation and the Alpha male during sexual cycling. Since the subordinate male served as a focal point for the activities of infants and juveniles, females appeared to benefit from their association with him during lactation. In addition, data suggested that the subordinate male, having established bonds during lactation, attempted to maintain these bonds into the females' periods of sexual cycling. It is hypothesized that the existence of these male-female bonds in multi-male primate groups produces a social structure characterized by a polygynous mating system. Data suggest that male-female relationships are best understood not by examining sexual consortship alone but by considering sexual behaviour within the context of social interactions throughout all reproductive states.