The arrival of rotting boats crowded with hundreds of individuals exhausted by a difficult crossing in wretched conditions is a powerful image too often seen in the Italian newspapers. In the majority of cases, the sea crossing is only a small part of a long and eventful journey. The cross-Mediterranean flow of migrants without papers originates on the southern and eastern shores of the Mediterranean Sea, but it includes migration from several continents. Many Mediterranean countries have become transit routes as the main objective of the sea journey is to cross the most protected border, that of the Schengen area. In these countries migrants become clients of illegal organizations: they pay for a service and subject themselves to rough treatment, with high risk for their personal safety. The article reconstructs the routes and the organization of the travels which irregularly cross the Mediterranean Sea to reach Italy. Different migration flows and their evolution are presented: the case of short crossings from Albania at the beginning of the 1990s; the departures from Turkey, Syria and Lebanon at the end of the 1990s; the passage from the Suez Canal; the long-distance journeys from West Africa; and finally the landings in Lampedusa, from Libya, which is currently the most favoured route. Focus is placed on the organizations that run the illegal entry routes, and on the institutional reactions at play to stop these irregular movements, considering both the Italian and the international sides.