In the years since the SDR was created, the international monetary system has experienced a number of profound changes. The present paper sketches the effects of these changes on perceptions of the role that the SDR can and should play in that system. It first briefly reviews the problems of international liquidity inherent in the Bretton Woods gold exchange standard and summarizes the views that were held when the SDR was established regarding the potential contributions of the new asset to the solution. It then considers how a number of structural changes in the international monetary system, in particular the suspension of gold convertibility of the U.S. dollar, the switch from a fixed to a more flexible exchange rate system, and the evolution of international capital markets, have affected the mechanisms through which international liquidity is provided. The discussion leads to a review of how the perceived role of the SDR has changed as a consequence of changes in the economic environment. The main issues raised in this review are then summarized.