Highly polymorphic major histocompatibility complex (MHC) genes are thought to play a central role in the choice of genetically compatible sexual partners in some vertebrates, although the evidence is variable across species. Here, we investigate the association between similarity in the MHC region and sexual preferences in the bank vole Myodes (=Clethrionomys) glareolus (Arvicollinae) in a laboratory setting. Females in post-partum oestrus were given the choice between the scents of two males in a Y-maze. Both males were unrelated to the female, but differed in their MHC similarity to the female. We found that females spent more time near the scent of MHC dissimilar males than those, with whom they shared MHC alleles. This suggests that bank voles use MHC-related cues to choose compatible mates.