In Italy, since the 1980s, there have been significant migratory flows of citizens from countries where economic, political and social conditions do not allow for survival. They form part of the foreign population resident in Italy, estimated to be over 5 million people, of which nearly 700,000 in Lazio, and who live mainly in large metropolitan areas such as Rome, Milan, Turin. Only half of this population is engaged in a registered work. Less than one tenth has a regular residence permit for work, family reunification, political asylum or study. Most foreigners come from countries with strong migratory pressure: in Rome among the most represented populations are Egyptian, Moroccan, Tunisian. For a cultural, historical and religious continuity in the presentation, reference is also made to the people from Algeria and Libya, thus completing the framework of migration flows between North Africa and the Rome Metropolitan Area (RMA). The North African population officially resident in RMA, so the visible one, was (2016) about 20,000 units. These data refer to individuals officially resident in Rome and overlook the situation of these invisible flows, because unregistered, who landed fortunately on Italian coasts, after stressful experiences crossing the Mediterranean, stopped in Rome for more or less shorter periods. In order to examine the invisible flows, the patient registration data that were hospitalized at the Accident and Emergency (A&E) Departments of the main RMA hospitals (2000-2015) was examined. Particularly interesting is to consider the invisible flows of citizens of North Africa as the phenomenon has undergone significant transformations over the last 15 years. Crossings of the Mediterranean by irregular immigrants continue but the affected ethnic groups have changed and the flow of North Africans has long exhausted. In order to examine the phenomenon, and try to make the best use of data apparently unreliable, data (2000-2015) concerning the population of young immigrants (17-35 years) will be examined in relation to the total population of immigrants from North Africa countries that will be confronted with RMA residential areas, and with A&E Departments admissions. The presentation will be based on some of the results of the research projects on Youth Mobility: maximizing opportunities for individuals, labour markets and regions in Europe (YMOBILITY) and Emergency Department as an epidemiological observatory of human mobility: the case of Rome Metropolitan Area (EMAHM)