Persons over the age of 65 years are the fastest growing segment of the U.S.population. In the next 30 years, they will comprise more than 20% of the population. Fifty percent of all cancers occur in this age group, and therefore, there is an expected rise in the total cancer burden. Data are becoming available that will better guide the use of chemotherapy in the older patient population. In this paper, information regarding age-related physiologicchanges and their relationship to pharmacology, functional status, and hematopoiesis is presented. The adjuvant treatment of breast and colon cancer, as well as the primary therapy of aggressive non-Hodgkin lymphoma is reviewed. The treatment of more advanced breast, ovarian, and non-small cell lung cancer is also discussed.