It is important to understand wildlife disease and the mechanisms underlying disease resistance because disease is among the top five causes of species extinctions world-wide. The ability to combat disease is largely controlled by diversity at key disease-resistance-genes, such as those of the Major Histocompatibility Complex (MHC). Many genes within the MHC play a central role in pathogen recognition and are therefore one of the most important genes involved in disease resistance. Higher diversity at MHC genes equates to a greater range of pathogens that the immune system can identify and act upon. As a result, MHC genes are extremely valuable markers for population health and adaptive potential in conservation biology. However, knowledge on diversity at genes influencing disease resistance, and the mechanisms generating and maintaining this diversity, is conspicuously lacking in reptiles. As Australia has an extremely high diversity of reptiles this is a critical issue for wildlife conservation in this country. Given their role in the immune system, pathogen-mediated selection is considered to be the main selective force maintaining diversity at MHC genes. However, sexual selection can also play a role through non-random mating associated with external cues like pheromones or ornaments that signal MHC gene diversity. In some cases sexual selection may even have more influence on MHC gene diversity than pathogen-mediated selection. How diverse are dragon lizard MHC genes and which selective forces play a role in maintaining their diversity? We aim to address these gaps in the literature using an Australian dragon lizard and disease-resistance-genes of the MHC as a model system.