For many years after its formation in 1920 the Communist Party of Australia (CPA) was loyal to the Soviet Union and the brand of Marxism practised by the Communist Party of the Soviet Union (CPSU). But in the mid-1960s the CPA became increasingly critical especially after the Soviet invasion of Czechoslovakia in August 1968. This stance was linked to a new kind of theory and practice which later saw the CPA begin to embrace an emerging radical politics which included support for feminism, environmentalism and gay liberation. This chapter examines the CPA’s evolution from 1966 to 1971 and argues that the break with Moscow arose within a wider internal debate about the achievement of socialism in Australia and the relevance or otherwise of orthodox Marxism. That is, it will be argued that the CPA’s domestic political practice was at least as central as issues of international affairs.