In overviewing the (scant) empirical evidence gathered on and the literature written about New Social Movements (NSM's) in Belgium this article tries to buttress three general propositions. First, the NSM' highlight a general tendency among social movements today of a thoroughgoing dissociation of the mobilizational potential on the one hand and organizational (decision making) power on the other hand. Second, the NSM's in Belgium have helped substantially in raising participation levels, broadening the action repertoire of the citizens and changing the nature ofparticipation. Third, although participation levels in Belgium are still beneath the West-European averages, the NSM's consitute in Belgium - with the New Right as their direct opponent - a new cleavage line in an altogether weakening system of cleavages.