Cognitive dysfunction following chemotherapy is an adverse treatment effect that impacts the quality of life for many cancer survivors receiving this adjuvant therapy. A strong body of evidence now indicates that that the initiation of a regular exercise program, at levels that are readily achievable by most adults (3-5 d/wk, 30-45 min/session), can improve cognitive function. Importantly, the domains of cognitive function that are enhanced by exercise participation are the same domains that are negatively 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 (n=60), 2) explore possible mediators and moderators of the intervention on cognition in order to begin to understand how the intervention may work and for whom it may be most effective, 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 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.