Cancer is the second most common cause of death among those aged ≥65 years, and is a major cause of morbidity. There is some evidence that screening, by detecting precancerous lesions in asymptomatic patients, is effective in reducing cancer-related morbidity and mortality among older men and women. The objectives of the current review article were to identify some of the barriers to and opportunities for research in cancer screening among older individuals. Using expert opinion, the authors developed a taxonomy of barriers to research among those aged ≥65 years at 3 levels: the macro (policy and population), the organizational and provider, and the interindividual and intraindividual. There are numerous barriers to high-quality screening research among older individuals, across all 3 levels of the taxonomy. Overall, there are limited evaluations of repeat adherence; follow-up for positive findings; screening, diagnostic, and treatment delays; and access to and acceptance of screening among those aged ≥65 years. There are particular barriers to research in colorectal cancer screening. There has been limited development and testing of evidence-based and theory-based intervention approaches to enrich screening adherence over time by those aged ≥65 years in which screening has demonstrated effectiveness. Professional groups differ in their recommendations for screening older asymptomatic patients, and implementation varies across healthcare systems in the US and the UK. The authors propose an agenda for cancer screening research in older populations, based on US and UK experiences. Cancer 2008;113(12 suppl):3493–504. © 2008 American Cancer Society.