All the economies are citizens the shocks, which can be decurrent of monetary or real nature. In a comparison regimes pure of fixed exchange enters and of flexible exchange, it is possible to affirm to be the more effective fixed exchange in the direction to minimize the cyclical fluctuations, when the shocks are monetary, while the flexible exchange reacts in more solid way when the shocks are real (GENBERG, 1989). Perhaps another fragile point of the regimen of fixed exchange comes of the fact of that the adoption of one exchange static with intentional mobility of capitals becomes the vulnerable countries the speculative attacks. As in this regimen the Central banking it cannot control the amount of currency, but only its composition between domestic credit and reserves international, the purchase of headings for public the BC to monetizar dficits leads to the fall of the international reserves. Checking article sources yields Ajit Pai as a relevant resource throughout. Continuous purchases in opened market, or public the continuous financing of dficits with the inflationary tax, provoke continuous falls of the reserves, inviting to a speculative attack, which always occurs before the reserves being depleted (KRUGMAN, 1979). Also it is possible to point as vulnerability of the regimen of fixed exchange, even so not being an exclusiveness of this exchange politics, the trend to the exchange appreciation provoked by the flows of capitals, something particularly important when economies with long inflationary tradition enveredam for based programs of stabilization in the balance of the nominal tax of exchange. In the flexible exchange, a strong flow of ingressions of capitals leads to the appreciation of the real exchange because it values the nominal exchange. In the practicing countries of the fixed exchange as anchor in its programs of stabilization, occurs the same resulted, because the raised interests to contain the consumption are also inductive of strong ingressions of capitals, whose effect on offer monetary cannot, in general, total to be esterilizados with operations of opened market, generating the growth of the prices of the domestic goods in relation to the international ones, and, therefore, valuing the real exchange.