This study dealt with factors affecting agonistic communication in rhesus monkeys. Definitions were given for various postures, facial expressions, and vocalizations. The data revealed that such communications depended at least upon the following factors: 1. Age Dominance displays (yawning, threats) increased with age while fear grimaces and vocalizations decreased with age. 2. Sex Dominance displays occurred more often and fear grimaces and vocalizations less often in males than in females. Crook tail should be used with caution as a measure of dominance, at least in subadult rhesus monkeys. The average duration of crook tail seemed to be a more relevant index of dominance than the frequency of crook tail. 3. Rearing Motherless mothering and peer deprivation depressed displays of dominance, while rotated mothering increased dominance displays. Repeated separation produced submissive and dependent behavior; however, calls for social contact (coos) were emitted much more frequently in these animals. This vocalization change was probably a product of social learning. 4. Social stimulus Displays of dominance and submission were dependent upon the nature (i.e., size, age, hostility) of the social partner. 5. Adaptation to the social partner Dominance related behaviors decreased and calls for friendly contact increased as the animal became more familiar with a strange social partner.