The present investigation looks at the recent success of ethnolinguistic politics as, largerly, the outcome of friction betweèn the existing -pattern of political integration and a set of relatively new · socio-economic conditions. The development of the latter is part of what may be implied in the phrase «post-industrial society». The Belgian pattern of political integration is characterized by very low levels of differentiation between the parties, the administration and the voluntary organizations. It implies a mode of political participation in which the recent developments in the organization of labor, expansion of the tertiary sector, geographical mobility and urbanization lead to political marginality for the groupsconcerned. This marginality expresses itself in support for ethnolinguism which serves as an alternative route to political integration. This theory is evaluated and substantiated on the basis of an ecological analysis of the success of an ethnolinguistic party (the Front Démocratique des Francophones) in the 1970 and 1976 communal elections.