This manuscript summarizes the break-out session held on how does koala retrovirus (KoRV) induce disease at the genomic level at the Koala Conservation Workshop: The koala and its retroviruses: implications for sustainability and survival held at San Diego Zoo, April 17–18, 2013. The goals of this break-out session were to review current knowledge in this area and identify studies required to fill important gaps. KoRV is a gammaretrovirus with close similarity to MLV and FeLV, well-characterized pathogens of the laboratory mouse and the domestic cat. The parallel wth FeLV is particularly striking as cats harbor related endogenous retroviruses that share receptor specificity with endogenous KoRV. Also, transmission and pathogenesis of FeLV in its natural host is well understood and the virus is routinely controlled by measures that include vaccines. Alternative models for the roles of endogenous and exogenous KoRV in disease were discussed and prospective studies required to test these hypotheses were outlined.