Cancer is a genetic disease. To date, translational cancer genomics has focused largely on somatic alterations, driven by the desire to identify targets for personalized therapy. However, therapeutically relevant information is also latent within the germline genome. In addition to cancer susceptibility, alterations present in the germ line can determine responses to both targeted and more traditional anticancer therapies, as well as their toxicities. Despite the importance of these alterations, many algorithms designed to analyse somatic mutations conversely continue to subtract information on germline genetics during analysis. In the light of low actionable yields from somatic tumour testing, a need exists for diversification of the sources of potential therapeutic biomarkers. In this Review, we summarize the literature on the therapeutic potential of alterations in the germline genome. The therapeutic value of germline information will not only be manifest as improvements in treatment but will also drive greater levels of engagement and cooperation between traditional oncology services and familial risk management clinics.