This article briefly reviews various issues concerning the functioning of the International Monetary System after 1971, such as flexible exchange rates and fixed exchange rates, optimal currency areas, increasing capital movements, exchange rate volatility, currency crises, external deficit of the United States. Even in the absence of an a priori design, the sequence of these problems has paved the way to the recent proposal of Mundell and Cooper for a world currency. This proposal is not a simple way out of today's concerns. Nevertheless, it suggests the possibility of a better future