For many years, there has been spirited debate as to the relative importance of environmental and genetic factors in the pathogenesis of cancer. Current efforts to annotate the human genome for germ-line genetic variants should establish the foundation for dissecting the contribution of genetics to the risk for cancer susceptibility. Population-based studies should be conducted to determine the influence of germline genetic variation on cancer outcomes, including the efficacy of anti-cancer drugs and the risk for life-threatening toxicities. Although we are early in the investigation of the influence of germline genetics on cancer outcomes, it is likely that, in the future, it will be possible to individualize therapeutic interventions. In turn, knowledge of genetic risk factors could afford opportunities for prevention, early intervention and minimization of deleterious toxicities associated with cancer therapy.