A hundred South Koreans are visiting the North Korean capital, Pyongyang, for the first time since the peninsula was divided in 1945.
By Charles Scanlon
BBC correspondent in South Korea
They left on the first commercial flight between the two Korean states.
South Korean tourists have already travelled to an isolated mountain resort in North Korea in recent years, but this is the first time they have been able to see the capital of the communist state.
The tourists will spend five days in the remote North
Nearly 120 people signed up for the five-day tour, at nearly $2,000 a head.
For that they will be able to see monuments to the ruling Kim dynasty, visit a model farm, the railway station and see a state-run kindergarten.
A company official said the idea was to let South Koreans see how Northerners live.
But they are not expecting to be allowed much contact with ordinary citizens.
Despite growing economic links, the North Korean regime goes to extraordinary lengths to block outside ideas and information.
The tourists travelled on the first ever inter-Korean commercial flight
One of the tourists said she had not been able to see relatives in the North for half a century, and did not expect to be allowed to see them during the visit.
Another, a professor of North Korean Studies, said he hoped the visits would help unification.
The travel company, Pyeonghwa, is an affiliate of the Unification Church of Moon Sun-myung, which recently opened the first car assembly plant in North Korea.
It hopes to take 2,000 visitors to Pyongyang before the end of the year.