The CPI(M) was formed at the Seventh Congress of the Communist Party of India held in Calcutta from October 31 to November 7, 1964. The CPI(M) was born in the struggle against revisionism and sectarianism in the communist movement at the international and national level, in order to defend the scientific and revolutionary tenets of Marxism-Leninism and its appropriate application in the concrete Indian conditions. The CPI(M) combines the fine heritage of the anti-imperialist struggle and the revolutionary legacy of the undivided Communist Party which was founded in 1920. Over the years, the Party has emerged as the foremost Left force in the country.

The CPI(M) has grown steadily since its formation in 1964. The membership of the Party, which was 118,683 at the time of its formation, has grown to 814,408 in 2002. The Party has sought to independently apply Marxism-Leninism to Indian conditions and to work out the strategy and tactics for a peoples democratic revolution, which can transform the lives of the Indian people. The CPI(M) is engaged in bringing about this basic transformation by carrying out a programme to end imperialist, big bourgeois and landlord exploitation. The CPI(M) as the leading Left party is committed to build a Left and democratic front which can present a real alternative to the existing bourgeois-landlord policies.

The Party has been able to effectively withstand the imperialist propaganda offensive in the aftermath of the setback and reverses to socialism internationally. While various communist parties had changed their names and abandoned the ideology of the working class, the CPI(M) maintained its ideological and political unity. This is not to deny the fact that these developments should lead to a reassessment and fresh look at the experience and history of the Communist movement. The intense ideological debate that ensued in the background of these events have only strengthened the commitment of the CPI(M) members and cadres to the cause of the Party and the science of Marxism-Leninism. The 14th Congress of the CPI(M) adopted an ideological resolution spelling out the CPI(M) understanding on these developments. It marks the beginning of the reappraisal of past experience, learn from it, and renew our Marxist outlook to meet contemporary challenges.