This paper presents the findings of an IMF task force set up to investigate issues related to the causes and consequences of deflation, as well as the the risks in individual economies and on a global scale. It focuses on four aspects: an analytical framework regarding the measurement, determinants, and costs of deflation; historical experiences of deflationary pressures in the nineteenth century and during the Great Depression, along with the recent experience of Japan and China; risk assessment issues; and policy options available.