Banners, as well as national and communist party flags, adorned many buildings on Friday but there were few other signs of festivities in Vientiane, with officials discussing the challenges ahead as well as the achievements of the regime.
"We have ensured the country's political stability and maintained public order," President Khamtay Siphandone said in his speech.
The communists took Vientiane in August 1975 less than four months after the fall of the US-backed South Vietnamese regime in Saigon, now Ho Chi Minh City, and founded the Lao People's Democratic Republic on 2 December.
People linked to the former US-backed government were sent to re-education camps, the economy was collectivised, and the country closed its doors on the West.
Khamtay pledged to get his
country out of poverty by 2020
Only in the early 1990s did Laos begin to slowly open up. Now a country of 5.6 million people, Laos joined the Association of Southeast Asian Nations (ASEAN) in 1997, introduced economic reforms and accepted foreign aid, still a mainstay of its economy.
"Over the past 30 years, we were able to develop the economy and maintain a consistent pace of growth," said Khamtay, whose speech greeted with scant applause from the crowd.
In a voice that sounded faint at times even through the loudspeakers, he said Laos would emerge out of the list of least developed countries by 2020.
He said the regime planned to lift the country out of least-developed status "by enhancing the strength of all economic sectors based on the market-oriented mechanism, together with seizing external cooperation and assistance."
Women in traditional dress
attended the celebrations
He also acknowledged the "support from the international community, including friendly countries, the United Nations system, financial organisations and non-government organisations."
As soon as Khamtay's speech ended, the crowds, including around 3000 men and women from the armed forces, marched away hurriedly.
Donors say Laos had some achievements to show already.
"There is something to celebrate here," said Finn Reske-Nielsen, resident coordinator of the UN Development Programme.
There had been a "very significant reduction in poverty", with 30% of people now deemed to be living below the poverty line, he said.