Suggestions that Lenin's body might be removed and buried have surfaced periodically since the end of communist rule in 1991.
But post-Soviet leaders have so far decided against the measure which would enrage leftists.
About 200 activists, several of them holding red Soviet flags, trooped across the cobblestones and laid wreaths before filing through the mausoleum on the 80th anniversary of Lenin's death.
"We must safeguard this place as a sacred site of our fatherland," Communist Party chief Gennady Zyuganov said outside the red marble structure, atop which communist leaders reviewed mass marchpasts until the collapse of the Soviet Union.
"No normal thinking person could possibly even speak of such a proposal, let alone examine it," he told reporters at the foot of the Kremlin walls.
"Anyone with a shred of conscience must respect history as it is."
Lenin loses pull
Alongside Zyuganov stood Nikolai Kharitonov, one of a number of challengers taking on heavily favoured Russian President leader Vladimir Putin in March elections.
Lenin has become less popular in
Zyuganov, who has lost two presidential polls, chose not to stand after his party suffered heavy losses in a December parliamentary poll.
News reports in recent weeks quoted experts as saying that modern embalming techniques ensured that Lenin's body, lying behind bullet-proof glass, could remain intact for many years.
Lenin died aged 53 virtually paralysed.
Lenin's popularity has been dipping of late, with surveys showing that 36% of Russians expressed "sympathy" for him in 2002 compared to 70% in a survey conducted in 1990.