Large brains and great intelligence are metabolically costly, but the social complexity hypothesis suggests that these traits were favored nonetheless in primates by selection pressures associated with life in complex societies. If so, then cognitive abilities and nervous systems with primatelike attributes should have evolved convergently in nonprimate mammals living in large, elaborate societies in which social dexterity enhances individual fitness. Societies of spotted hyenas (Crocuta crocuta) are remarkably similar to those of cercopithecine primates with respect to size, structure, and patterns of competition and cooperation. These similarities set an ideal stage for comparative analysis of social intelligence and nervous system organization. As in cercopithecine primates, spotted hyenas use multiple sensory modalities to recognize their kin and other conspecifics as individuals, they know that some group-mates are more valuable social partners than others, they recognize 3rd-party kin and rank relationships among their clan-mates, and they use this knowledge adaptively during social decision-making. Examination of the available data strongly suggests convergent evolution of intelligence between spotted hyenas and primates. Evidence that less gregarious members of the family Hyaenidae lack some of the cognitive abilities found in spotted hyenas would provide further support for the idea that social complexity favors enhancement of intelligence in mammals.