Italian Rationalism held a specific position in the Modern Movements of Architecture, due to the fact that Italian Rationalism could not totally escape from the classical tradition of Italy. Until the seventies, Italian Rationalism had been criticized for having made no contribution to the progressive aspects of the Modern Movements owing to the very keeping of tradition. After the seventies, however, there emerged a movement which tries to reinterprete the Modern Movements of Architecture in relation to tradition and under this new situation, Italian Rationalism is believed to have a historical possibility of unifying tradition with modernity. This study is to show how Italian Rationalism struggled with the issue of tradition, why Italian Rationalism was under-evaluated and which historic lesson we can learn from it in the contemporary days of the revivalistic Post-Modernism.