The world's population is aging. Older age is associated with an increase in the incidence of cancer, especially cancer of the breast, lung, prostate, and colon. The management of older patients with cancer is biased by the simple fact of their chronologic age. Underscreening, understaging, less aggressive therapy, lack of participation in clinical trials, or no treatment at all reflect this bias. Although an age-related reduction in the physiologic function of many organs occurs with age, these are not contraindications to treatment with surgery, radiation therapy, or chemotherapy. Chronologic age alone should not be used as a guide for cancer management. Rather, physiologic function or existence of comorbid conditions should be major factors in determining treatment. As a result of the impending need for improved cancer management in older persons, a new subspecialty is evolving: geriatric oncology. This field stresses an important interaction between geriatricians and oncologists, development of research directed at the problems of cancer in older persons, and education at all levels with respect to cancer prevention, cancer detection, and cancer therapy. Physicians and oncologists need to be prepared for the projected increase of cancer in older persons.