This paper is an analysis of the way in which the changes in the labour market and in the occupational structure in Europe affect the situation and the role of Third World migrants. The author singles out, first, the main differences between the present migratory waves and the intra-European migrations of the 1960s and 1970s. Not only are the numbers of nationalities and ethnic groups who participate in the new migratory experience greater now than before, but also the destinations are different. At the time of the great intra-European migrations the receiving areas were the most developed European industrial countries: now Spain, Italy, and Greece also attract a large number of migrants from the Third World. Intra-European migrations were industrial migrations because manufacturing and building industries were the most important and growing economic activities. While industrial employment increased, the working class and the industrial conflict were the basic factors of those societies. Present-day migrations are postindustrial migrations. Immigrants work mostly in service activities and not infrequently in the informal economy. In any case migrant workers are located in the secondary labour market. The picture is made more complex by the fact that many immigrants are alegal or illegal because of the restrictive immigration policies in European countries. The casual character of the migrants' occupations, coupled with the fact that some of them are not settled, but keep migrating within the hosting countries. makes more difficult their union organization. Besides that, the forms of solidarity which are developing now are less and less class based, but are based on ethnic and religious bonds.