The role of social experience in recognition of individuals and their odours is not well understood. In a previous study, hamsters discriminated between the odours of their familiar litter mates, but they did not discriminate between the odours of two males or two females from a different litter that were unfamiliar to them. In this paper the role of social experience in discrimination between odours of male litter mates is examined using habituation techniques. Males, tested 1.5–2 mo after separation from their litter mates, discriminated between the flank gland odours of their foster brothers, but they did not discriminate between flank odours from their unfamiliar brothers that had been reared by another mother (Expt. 1). In Expt. 2, adult males did not discriminate between the flank gland odours of two males from a different litter after a week of exposure across a barrier to their sights, sounds, and odours, but subjects did discriminate between the odours of these same males after five brief encounters with them. A month after the encounters, however, subjects no longer discriminated between these odours. In contrast, adult males discriminated between the flank odours of their brothers 9 mo after separation from them (Expt. 3). These results suggest that hamsters must have direct interactions with closely related individuals to discriminate between their odours because the odours of close kin are so similar. Experience with nest mates results in long-lasting memories for their odours.