The House Mouse Group analyses allelic variation in four speciation genes (Prdm9, Hstx and Slx, Sly) causing sterility or sperm defects in hybrids between two house mouse subspecies, Mus musculus musculus and M. m. domesticus. Specifically, we ask what fraction of interacting alleles are associated with hybrid defects of spermatogenesis in laboratory intersubspecific crosses utilising a collection of 80 wild-derived mouse strains (unique in the world).