Neural precursors that are found in the subventricular zone and dentate gyrus of the adult brain might be useful in cell replacement therapies for neurological disorders. The development of pharmacological drugs that would increase production of new neurons would be facilitated by identification of the endogenous or natural molecular regulators of adult neurogenesis in vivo. This review discusses known endogenous regulators of the cellular events that are required for functional neurogenesis in adult animals. These steps include proliferation of stem cells and progenitors, survival and migration of new neuroblasts, differentiation into mature neurons and functional integration into existing neural circuits. Various treatments have been shown to enhance neurogenesis and neuroblast migration in adult rodents, raising the possibility that these resident neural stem cells could be used to treat people with neurological disorders. This review also highlights some of the potential problems and limitations that may arise when considering such therapies.