Abstract: Nestmate recognition is the process by which individuals discriminate between nestmates and con- and hetero-specifics. Nestmate recognition is based on recognition cues, which include cuticular hydrocarbons (CHCs). Models of nestmate recognition predict that recognition decisions are based on the overlap of recognition cues. Colony recipients assess cue differences by comparing an individual's Chc profile to an internal template, which is based on the colony-specific cues. The behavioral response to this assessment depends on cue similarities or differences with the template. Ants show graded responses to cue differences. More recent models of nestmate recognition include adjustable thresholds that account for graded responses and intra-colony individual variation in behavioral responses towards non-nestmates. Ants display differing levels of aggression towards conspecifics under different contexts, which suggests that nestmate recognition is context-dependent. Here, we review models of decision rules and the role of CHCs in nestmate recognition. We discuss the role of ecological and social context in nestmate recognition, and explore future directions of research for the field.