The discovery of active adult neurogenesis in mammals, a process of generating functional neurons from neural stem cells, suggests that the adult brain is more dynamic than once imagined. The coincidence of this phenomenon occurring in the hippocampus, a region critical to the learning process, begs the question of whether adult neurogenesis is involved in memory formation. Here, the authors review rapidly accumulating evidence showing a strong correlation between certain types of memory functions and adult neurogenesis in the hippocampus. Establishment of the potential link between memory formation and adult neurogenesis is instrumental, at a basic science level, to understand the function of neural networks and is essential, at a clinical level, to develop effective therapies for various cognitive dysfunctions.