The discovery of neurogenic response subsequent to brain injuries has led to the hypothesis that the expansion of the pool of endogenous progenitors could augment the regenerative capacity of the damaged areas. However, it occurred that endogenous spontaneous neurogenesis is insufficient for replacing the lost neurons and to achieve global repair, particularly in aging brain. Until today, a great effort has been made attempting to promote "reactive neurogenesis" more successful. It was found that small chemical molecules exert stimulation of neurogenesis and probably might help to induce neuronal endogenous cell replacement in various neurological diseases. In this review we briefly highlight the current data regarding effect of brain ischemia and age-related neurodegenerative diseases on neural stem cells in situ and potential therapeutic effect of their stimulation.