The idea that diet and nutrition play an important role in carcinogenesis is not new. Much has been learned in this area during the past several decades through traditional epidemiological methods, but many questions remain unanswered. The present is a particularly exciting time for researching how genetic and nutritional factors interact to influence the risk of various cancers. With new methods that help us better identify genetic susceptibility, clearer answers are likely to emerge in the field of nutrition and cancer. The first part of this chapter will briefly summarize the role of various epidemiological strategies that are used to understand cancer causation and prevention. In particular, the strengths and weaknesses of various epidemiological approaches will be described. Building upon this, the second part of the chapter will examine how our evolving understanding of genetic susceptibility can be integrated into traditional epidemiological methods to help refine our understanding of diet, nutrition, and cancer.