Singapore PM Lee Hsien Loong has fainted as he was delivering a speech during a National Day rally.
The live broadcast was suspended as doctors attended to him.
Mr Lee had been "unsteady because of prolonged standing, heat and dehydration," a statement from his office said. "His heart is fine and he did not have a stroke."
He later resumed his speech to applause. Lee Hsien Loong, 64, has been in office since August 2004.
Last year, he had surgery to remove his prostate gland. He was diagnosed with lymphoma in the 1990s but recovered.
Mr Lee's People's Action Party (PAP) has been in power since 1959, when Singapore was still a self-governing British colony.
A former army officer and Cambridge-educated mathematician, he followed his father Lee Kwan Yew into politics in 1984 at the age of 32.
As he resumed his speech, he said his government's "top priority" would be preparing for succession.
Mr Lee said a new prime minister "must be ready" to take office after the next general election.
The PAP won a decisive victory in last year's elections. Elections in Singapore are held every five years.
As prime minister, the younger Mr Lee has launched policies to build a competitive economy, introducing new programmes to upgrade the education system, investing in research and development and transforming the city-state.