Following the recent financial crisis, major central banks have introduced several types of unconventional monetary policy measures, including liquidity and credit facilities, asset purchases and forward guidance. To date, these measures appear to have been successful. They restored market functioning, facilitated the transmission of monetary policy and supported economic activity. They have potential costs, however, including challenges related to the greatly expanded balance sheets of central banks and the eventual exit from these measures, as well as the vulnerabilities that can arise from prolonged monetary accommodation.