Approximately 60% of cancer incidence occurs in adults aged > or =65 years, yet older patients often are not accorded access to treatment trials. Therefore, providers remain uninformed about clinical and behavioral responses of older patients with cancer to cancer treatment. The objectives of this article were to provide a broad overview of some of the dimensions of cancer treatment in the elderly and to raise issues for behavioral research. The literature was reviewed in general for cancer treatment and specifically to address areas such as comorbidity, function, adverse events, palliation, side effects, social and psychological factors, cognition, and provider behavior. The authors address the importance of behavioral research and discuss issues for behavioral researchers in the context of cancer treatment. Few studies were identified that were specific to behavioral research. The results indicated that chronological age alone is an inadequate indicator to determine responses among older patients to cancer treatment. When they are selected carefully, older patients can benefit from treatment or palliation. More research is needed to define clinical and behavioral criteria for the inclusion of older patients in treatment trials.