Theoretical and field studies suggest that inferior competitors may be able to avoid costly agonistic interactions, although the mechanisms involved are poorly understood in lizards. The "Dear enemy recognition" theory proposes that higher tolerance among familiar than among unfamiliar conspecifics may reduce costly interactions. Male lizards Lacerta monticola are able to discriminate between familiar and unfamiliar conspecific males through chemical signals alone. To better understand the implications of this discrimination ability, we performed a laboratory experiment on the role of familiarity in social tolerance estimated as the degree of spatial proximity with no sign of aggressiveness between males with a size asymmetry. In natural conditions the outcome of neighbour-stranger interactions might be the result of asymmetries in residence. Therefore, we staged pairwise encounters between familiar and unfamiliar males in neutral terraria to avoid an interacting effect of residency asymmetry. The latency to the first time in close proximity was significantly longer when small males were faced with unfamiliar males. The time that unfamiliar lizards spent in close proximity was significantly lower than that with familiar males. Our design allowed us to conclude that there was a higher social tolerance among familiar individuals with a size asymmetry that was independent of residency asymmetry.