After some preliminary considerations on the composition of the Portuguese opposition currents, their strategy of action and the chronology of the confrontations, the article will examine the role of the Portuguese-Spanish border in the revolutionary opposition 1927 and 1936. Two periods emerge from the outset, the caesura of which takes place in 1931. During the first, the frontier serves as a place of concentration, awareness of the condition of exile and clandestine space for communication between The republican opposition of the interior and the exile. The implantation of the Second Republic in Spain transformed the frontier into a space for the preparation of revolutionary action, logistical and material support and retreat following the failure of the successive revolts against the military dictatorship and the Estado Novo. The material and financial support of the Azaña government, the Republican left and the Spanish Socialists contributes to the intensification of the revolutionary action of the Portuguese opposition and the evolution of the strategic action.