Cancer is primarily a disease of the elderly. Greater than 60% of new cancers occur in people aged >65 years, and 60% of the current 10 million cancer survivors are aged ≥65 years. Given these large numbers and the potential vulnerability of older adults, older cancer survivors have become an especially important group to study. This article discusses published research on the physical and mental functioning of older cancer survivors. In the first part, the authors reviewed studies of those who are newly diagnosed at the age of ≥65 years. The second part reviewed the research regarding long-term (≥5 years) cancer survivors who are aged >65 years, but may have been diagnosed at a younger age. Older survivors are likely to be more affected by cancer in terms of physical than psychologic function. However, comparisons with individuals without a history of cancer suggest that older cancer survivors may be faring worse physically and psychologically than noncancer comparison groups. For older cancer survivors, cancer occurs against a background of other chronic conditions and normal aging, and comorbidities and symptoms are important factors to consider. Limitations of the research were discussed, and recommendations for future research were provided. In particular, prospective studies with measures of functioning before cancer diagnosis and treatment, comparisons with age-matched noncancer populations, and interventions to reduce the impact of cancer on functioning are needed. Cancer 2008;113(12 suppl):3519-29. © 2008 American Cancer Society.