This paper refutes two ideas which have enjoyed broad approval in the texts devoted to the economic history of contemporary Spain: the first, which maintains that the depreciation experienced by the peseta in the transition to the twentieth century, in the sense that it raised the price of foreign currency, increased national barriers to imports; the second, the thesis that the payment in gold of certain customs duties, decreed at the beginning of the century, had the same protective effect, because of the important depreciation which separated the current value of the peseta from its gold parity at that time. The result of estimating the evolution of the real effective exchange rate of the peseta allows us to reject the first of the above mentioned protectionist implications. A rigorous study of the legislation governing the payment in gold of customs duties provides the basis for the rejection of the second. As a consequence, the paper draws the conclusion that the depreciation experienced at the end of the nineteenth century did not reinforce the trade defences of the internal market.