The powerful hold of the Italian Christian Democratic Party on post-war government entitles it to recognition as, in many ways, the most successful party in Western Europe. At the same time, the party is unique in having mass support whilst being identified with the political 'centre'. This study focuses on the relationship between these two aspects of Italian politics. The thesis starts by examining the importance of spatial terminology in analyses of Italian politics and proposes that 'the centre' has two distinct, if not unrelated, meanings. Drawing on this idea the thesis seeks to show that the evolution of the Italian party system can be understood through an analysis of two strategies which have dominated the Christian Democratic Party: the centre political strategy and the centre party strategy, each rooted in a different understanding of the centre. In studying these strategies, party competition is emphasised as the means by which Italian multi-partism has been bound into a unified, if internally contradictory system; whilst a study of economic policy-making exemplifies the complex inter-relationship which has seen this 'contradictory unity' contribute to the nation-building process. The thesis contributes to the debate about the nature of Christian Democracy and party competition in Italy, and to the debate within comparative politics about the nature of party system structure