Saturday's celebrations took place amid tight security - roadblocks were put up on all routes into the capital and everyone attending the ceremony was subjected to a body search.
The streets of Vientiane were draped in huge banners proclaiming the success of the Communist revolution.
Saturday's celebrations took place amid tight security - roadblocks were put up on all routes into the capital and everyone attending the ceremony was subjected to a body search.
In a televised speech, President Khamtay Siphandone said the party had brought political and social stability to Laos.
But correspondents say the country is facing rising economic problems, and a series of unexplained bomb explosions have dented the government's efforts to attract foreign investment.
'Socal tranquility'
In his address to the nation, President Siphandone said the Communist Party had "successfully foiled schemes of sabotage, embargo and attacks by opposing forces".
"Social tranquility and political stability have been insured," he said.
But the president made little reference to the series of bomb attacks which have troubled Vientiane over the past eight months.
It is not clear who is responsible for the explosions, but some diplomats in Laos think they could be linked to ethnic unrest in the country's northern mountains.
Others believe the attacks reflect divisions within the communist party leadership.
End of funds
Laos is rated by the World Bank as one of the least developed countries in terms of income and other social indicators.
The collapse of the Soviet Union meant the end of funds from Moscow.
The Communist Party was forced to open up the economy, but so far it has failed to attract much foreign investment.