Central banks have responded with exceptional vigour to the crisis by using their traditional interest-rate tools to their limits and deploying a wide range of unconventional measures. This paper documents these responses in a systematic way, reviews the evidence about their impact, and discusses the need to exit from these measures. Unconventional monetary policy measures appear to have been broadly successful in terms of improving conditions in financial markets and stabilising the real economy. In line with the improvement in functioning of financial markets, however, these unconventional measures should be gradually removed. Given the considerable changes in the size and composition of central banks' balance sheets, the exit will likely involve the combination of various tools. More challenging questions surround the decisions of when and how fast the current exceptional amount of stimulus should be reduced and then eliminated. A particularly important goal will be to preserve the hard-won anchoring of inflation expectations and dissipate any hypothetical fears that central banks? greater risk exposure and purchases of bonds issued or backed by governments might have reduced their independence regarding monetary policy decisions.