The purpose of the research was to demonstrate that comorbid health conditions disproportionately affect elderly cancer patients. Descriptive analyses and stacked area charts were used to examine the prevalence and severity of comorbid ailments by age of 27,506 newly diagnosed patients treated at one of eight cancer centers between 1998 and 2003. Hypertension was the most common ailment in all patients, diabetes was the second most prevalent ailment in middle-aged patients, and previous solid tumor(s) were the second most prevalent ailment in patients aged 74 and older. Although the prevalence and severity of comorbid ailments including dementia and congestive heart failure increased with age, some comorbidities such as HIV/AIDS and obesity decreased. Advances in cancer interventions have increased survivorship, but the impact of the changing prevalence and severity of comorbidities at different ages has implications for targeted research into targeted clinical and psychosocial interventions. © 2008 Elsevier Ireland Ltd. All rights reserved.