It has been suggested that primate mating and social behaviours may be influenced by variation in promoter region repetitive DNA of the vasopressin receptor 1a gene ( avpr1a ). We show that male mating behaviour does not covary in a simple way with promoter repetitive DNA in 12 Old World primates. We found that one microsatellite (−553 bp upstream) was present in all species, irrespective of their behaviour. By contrast, two microsatellites (−3956 and −3625 bp upstream) were present only in some species, yet this variation did not correlate with behaviour. These findings agree with a recent comparative analysis of voles and show that the variation in repetitive DNA in the avpr1a promoter region does not generally explain variation in male mating behaviour. Phylogenetic analysis revealed a GAGTA motif that has been independently deleted three times and involved in another larger deletion. Importantly, the presence/absence of this GAGTA motif leads to changes in predicted transcription factor-binding sites. Given the repeated loss of this motif, we speculate that it might be of functional relevance. We suggest that such non-repetitive variation, either in indels or in sequence variation, are likely to be important in explaining interspecific variation in avpr1a expression.