This thesis compares the foreign policy course undertaken by the German Social Democratic Party (SPD) and the Italian Communist Party (PC I) in the 1960s and 1970s. The thesis analyses where the foreign policy of the two parties converges and diverges, especially with regard to international detente, security policies, the Eastern bloc and European integration. The choice of a broad time frame is justified by the diverse timing and junctures of the SPD's and the PCI's revisionist course. Departing from the assumption that both SPD and PCI were characterised by their national roots and ambitions, the thesis seeks to arrive at party overlapping trends and conclusions as to how political parties address and overcome national and international constraints in spite of ideological divergences. One aim of the comparison is to examine policy revisionism and analyse its ongIns and motivations. Revisionism has its origins in a number of interrelated factors which are often not mutually exclusive. Policy shifts are every so often caused by ideological reconsiderations or a rethinking of, and adaptation to political, economic and social circumstances. The comparative method allows one to make general assumptions and draw parallels about the origins of revisionism, and relate them, where possible, to wider sections of the Western European Left. This process which occurred in the wider context of de-ideologisation was not distinctive to Italian communism or German social democracy but can be observed by examining Western European parties of the Left in general.