This paper examines differences in male affiliative associations and dominance relationships in atelin primates. Despite the occurrence of male philopatry in all three genera, male social relations varied considerably. The strength of male affiliations was attributed to differences in between group competition for access to groups of females, while the type of male dominance relationships was attributed to differences in within group competition for access to individual females. Female grouping patterns and the socionomic sex ratio appeared to be more important than group size in predicting the strength of between group competition and male affiliations. Male dominance over females appeared to be more important than estrus synchrony in predicting the type of within group competition and the presence of hierarchical or egalitarian relationships among males.