By its geographic position, Spain is the forced way of thousands of North African and Sub-Saharan citizens who try to arrive and to settle in Europe. But, in addition, in the last years, Spain has become a receiving country of foreign citizens who, in a situation of regularity or of administrative irregularity remain more or less continuously in its territory. This fact, along with the restrictive criteria imposed by the European norms and the visa requirement from May 1991 for Moroccan subjects, is the cause for the use of illegal or clandestine routes for immigration originating in Morocco, both for Moroccan citizens as well as Sub-Saharans who come to Morocco with the intention of crossing the Straits of Gibraltar. In this study the different mechanisms; mainly legal, used by the Spanish State in their fight against clandestine immigration, as well as its effects in the immigration originating from North Africa are analyzed