For decades the Communist Party of Australia was the most prominent organisation claiming to build a left-wing alternative to the Labor Party. Thousands of working-class activists inspired by socialist politics joined the Communists and helped to build the party into a major force on the left. However the Communist Party was stained by all the problems of Stalinism: support for authoritarian dictatorships, a reformist practice combined with a sterile Stalinised “Marxism”, and a hostility to genuine socialism from below. Ultimately it proved to be a barrier, rather than an instrument, for the building of revolutionary politics in Australia. For those of us wanting to build a socialist movement today understanding what went wrong with the Communist Party is vital.