In our daily practice, we provide clinical genetic consultation for patients at risk for hereditary cancers. The clinical characteristics of hereditary cancer syndromes in adults differ from those of hereditary diseases in children, although both involve genetic disease. One major difference is the difficulty in diagnosing hereditary cancers. Genetic testing has enabled us to diagnose HNPCC and familial breast and ovarian cancers. Another difference is the possibility to improve the outcomes of hereditary cancer syndromes by medical intervention. Intentional surveillance thus plays a key role in the management of hereditary cancer syndromes. These features make genetic counseling essential for hereditary cancer syndromes, including genetic testing and lifelong disease management. Networking among genetic disease specialists is particularly necessary. Clinical geneticists should be responsible for not only genetic disease but also for genomic information about cancer, with the ultimate goal of providing "order-made" medical consultation and services. Another important goal is the establishment of systems for the comprehensive care of patients and for the career development of specialists to provide regional-based care for persons who have or are at risk for hereditary cancers, including future generations.