Optimal community programs in cancer prevention and detection have as their goals the lowering of incidence, complications, and mortality from cancer in a population, and are characterized by efficiency, self-sustainability, and generalizability. Programs fall into three categories according to their degree of integration into the normal health-care system. "Extra-systemic" programs are temporary demonstration activities, which may have research goals. "Quasi-systemic" activities include public health department programs, worksite programs, and specialized centers such as breast screening centers. "Systemic" activities involve counseling and screening in routine medical practice. The greatest potential for reaching the indicated goals lies in facilitating systemic activities by allowing primary-care practitioners to define their own prevention goals, to make changes in their practices to address these goals, and to educate consumers of the need to demand preventive services.