In reviewing the models of potential reductions in rates of cancer incidence and mortality examined in this chapter, it is important to recognize that the benefits of primary prevention strategies against cancer (as distinguished from secondary prevention, i.e., screening) will lead to improvements in public health that go well beyond cancer alone, and these improvements may occur quite rapidly (Colditz and Gortmaker, 1995). A person who stops smoking today or who is prevented from starting smoking instantaneously reduces his or her risk of respiratory and cardiovascular problems, although the effect on the lung cancer risk may not be seen for many years (US DHHS, 1990). Similarly, a person who adopts a healthier diet and a more active lifestyle will reduce his or her risk of heart disease, stroke, diabetes (Knowler et al., 2002) and many other health problems that may have shorter latency periods than cancer.