We provide a brief review of the extant research on the influence of cardiovascular fitness training on brain and cognition. The review includes an examination of the non-human animal literature that has reported molecular, cellular, and behavioral consequences of fitness interventions. We relate this literature to human studies of the relationship between fitness and cognition, as well as the nascent literature on fitness influences on human brain structure and function with state-of-the art neuroimaging techniques. We also consider the important topic of participant adherence in clinical exercise trials. Finally, we suggest future directions for studies of cardiovascular fitness, aging, and neurocognitive function.