The immediate purpose of this handbook is to aid further research by stating, in a form providing handy reference, the facts concerning the Communist ideology in Hungary Following a narrative of the vicissitudes of that ideology prior to its power-phase - intended as a general introduction contributing to the proper assessment of the 1945-1965 period, which is the main concern of this book - the essential and relevant facts concerning the events, issues, organizations and opinions which have shaped post-war Hungarian Marxism Leninism are set out without indulging in lengthy commentaries and personal value-judgements. (Since even the 1956 revolution is treated thus - perhaps the most important, and certainly the most controversial single event of the above period - I should add that the reader interested in finding a detailed analysis and evaluation of the ideological relevance of that event may refer to my Individualism Collectivism and Political Power, The Hague, 1963, pp. 111-140. ) Despite the specificity of much of the data, sufficient translations of Hungarian titles, names and terms have been provided to render the present book useful for the investigator regardless of whether or not he reads Hungarian. But the fundamental purpose of this volume is to make a modest contribution to East-West understanding. It has arisen from the belief that the lessening of world-tensions is best served by understanding, and understanding is best served by objective information.