Research in humans and animals has shown that exercise improves mood and cognition. Physical activity also causes a robust increase in neurogenesis in the dentate gyrus of the hippocampus, a brain area important for learning and memory. The positive correlation between running and neurogenesis has raised the hypothesis that the new hippocampal neurons may mediate, in part, improved learning associated with exercise. The present review gives an overview of research pertaining to exercise-induced cell genesis, its possible relevance to memory function and the cellular mechanisms that may be involved in this process.