Persons over the age of 65 years are the fastest growing segment of the US population. In the next 30 years it will comprise over 20% of the population. More than 50% of all cancers occur in this age group and therefore, the total cancer burden is expected to rise. Data are becoming available that will better guide the use of chemotherapy in the older patient population. Understanding the physiologic and functional changes that occur with aging will assist in developing useful strategies in the elderly. Pharmacokinetic data on a broad spectrum of chemotherapeutic agents will be presented. Many of these agents seem to have a beneficial therapeutic index, particularly in older patients. There has also been an increasing trend toward the use of oral chemotherapy. Factors that must be considered in choosing chemotherapy include limitations of saturability of absorption, patient compliance, and the pharmacokinetic and pharmacodynamic changes that occur in older patients. Interpatient variability and age-related changes in drug metabolism are discussed. Careful attention to the physiologic changes with age and dose adjustments necessary for end organ dysfunction (renal, hepatic) are needed to ensure the safe administration of chemotherapy to older patients.