A substantial number of cancer survivors who receive chemotherapy report mild to moderate cognitive impairment following treatment. These impairments have been reported across a range of cancer types and chemotherapy agents. Adjuvant treatment has been reported to affect multiple cognitive domains, but three domains appear to be most strongly affected (i.e., executive functioning, declarative memory, motor function). Exercise participation, at levels that are readily achievable by most adults (3-5 d/wk, 30-45 min/d), preserves and enhances cognitive function. Importantly, domains that are enhanced by exercise overlap substantially with the domains adversely affected by chemotherapy. Accordingly, we propose a 2 year research program that seeks to develop and test a safe, simple, and effective exercise intervention to optimize cognitive function following chemotherapy. To begin this research, we will: 1) conduct a randomized exercise intervention trial among cancer survivors that report persistent cognitive problems following chemotherapy (exercise, n=30 vs. standard of care, n=30); 2) explore possible mediators and moderators of the intervention effect on cognition; and 3), conduct a cross-sectional study comparing cancer survivors enrolled in the trial (n=60) and matched controls (n=40) to evaluate the cognitive status among survivors in the intervention. We will employ a proven home-based exercise intervention and state of the art cognitive testing of relevant cognitive domains (e.g., Randt Memory Test, Trail Making B, Stroop task, T ask switching, Response compatibility) that we have used in preliminary studies. We hypothesize that six-months of regular exercise will enhance cognitive function among cancer survivors, and that cancer survivors reporting cognitive dysfunction will have lower objectively measured cognitive performance than adults who have not received chemotherapy. To our knowledge this study would be the first to examine the influence of regular exercise participation on cognitive function among cancer survivors that experienced cognitive difficulties following chemotherapy. Completion of this project will provide our research team with the necessary experience and intervention effectiveness information that will be used to conduct future more definitive trials.