The aim of this paper is to explore the possible influence of supply factors in the appearance of foreign trade deficit, with particular refe-rence to the Spanish case. For this purpose, we provide a brief exposi-tion of a theoretical justification for the said relationship, on the basis of M. Bruno's model (1976). Thereafter the possible compliance of the Spanish case with the conditions of the model is demonstrated, although the validity of the result is limited to the period 1985-1990. The result is favourable overall to the thosis as proposed, that is to say, a supply component exists in the genesis and maintenance of the foreign trade deficit of the Spanish economy.