Current epidemiologic and laboratory evidence suggests that nutritional factors may play an important role in chemoprevention, although the relative importance of that role for the various micronutrients and dietary constituents is still unclear. The complexity of this area of investigation and practice clearly requires knowledge of the relevant measurement tools, chemistry, biology, and food science, and also the limitations that must be considered in the interpretation of nutritional data. Despite the challenges encountered in translation to clinical research and practice, nutrition remains a promising area of chemoprevention, likely to yield important information and strategies with a large public health impact.