Studies in mice and humans have indicated that antibody responses to chlamydial-hsp60 are genetically predisposed (Gaur et al., 1999; Zhong & Brunham, 1992), but this is the first study to investigate associations between MHC and c-hsp60 antibodies and chlamydial disease in a free-living wildlife species, the koala. This evidence concerns the gene HLA-C and chlamydia trachomatis infectious disease.