13 females and 12 of 19 males present in a group of blue monkeys (Cercopithecus mitis stuhlmanni) mated promiscuously during an intense bout of sexual activity. Several aspects of their behavior are considered as mechanisms for determining mating patterns. Estrus synchrony coincided with a multi-male influx, allowing promiscuity. The length of stay and rank of an incoming male were correlated with his number of copulations in the group, while the original resident and highest ranking male was never seen to mate. Thus, although agonistic behavior, especially among males, affected mating success, it did not guarantee copulations. Adjustments of position relative to other individuals also affected who mated with whom. These and earlier observations suggest that there may be more than one way to be successful in mate competition, and lead us to question whether the kinds of behavior we observed have merely a reproductive function.