Summary — The author examines certain aspects of the problem of the legitimacy of political power in contemporary constitutions and gives an account of the changes in perspective that have occurred over recent years. Having taken into account when, by whom and in what ways the problem has been addressed, and having made a number of useful conceptual distinctions, the author analyses the problem in terms of representative institutions with particular reference to the case of Italy. The author attempts to demonstrate: (a) that in contemporary secularized political systems, the conception of legitimacy must of necessity be a relative one, and that this gives rise to an unstable legitimation of power based on consent to support for rulers on the part of the members of the political community; (b) that the foundations of contemporary representative democratic orders are in tension both in terms of the conception of legitimacy and in terms of the legitimation of the development of material conditions and of the transformation of the ways in which political conflict occurs; (c) that the Italian political system in particular, in this decade, has been subject to an intense crisis which has yet to be overcome and which has affected the political community, the regime, and the government authorities. The author concludes by claiming: (d) that the constitutionalist should not undervalue either the level of legitimacy or that of legitimation if he wishes to avoid betraying his own role as an interpreter of historically situated values; (e) that he should have a particularly strong commitment to the observance of procedural standards aimed at guaranteeing equality of opportunity in the competition internal to the political market.