The credit market turmoil that began in mid-2007 spilled over into a number of major currency money markets in early August 2007. This in turn triggered a variety of responses from central banks. Against this backdrop, the Committee on the Global Financial System (CGFS), in cooperation with the Markets Committee, convened a study group to examine how central banks adapted their liquidity operations in response to the emergence of money market tensions and how effective those responses were. Under the chairmanship of Francesco Papadia of the European Central Bank, the study group documented in this report the various central bank measures taken, assessed their outcomes, and set out seven recommendations for central bank liquidity operations. This report reflects the study group's experience and assessment up to end-April 2008, at which time market tensions were still persisting.