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