Banks perform various roles in the economy. First, they ameliorate the information problems between investors and borrowers by monitoring the latter and ensuring a proper use of the depositors’ funds. Second, they provide intertemporal smoothing of risk that cannot be diversified at a given point in time as well as insurance to depositors against unexpected consumption shocks. Because of the maturity mismatch between their assets and liabilities, however, banks are subject to the possibility of runs and systemic risk. Third, banks contribute to the growth of the economy. Fourth, they perform an important role in corporate governance. The relative importance of the different roles of banks varies substantially across countries and times but banks are always critical to the financial system.