NAIROBI, Kenya, Dec. 30 — Giddy Kenyans turned out by the hundreds of thousands today to see their longtime ruler, Daniel arap Moi, hand over power to a new president, Mwai Kibaki, who vowed to change the course of the beleaguered country. Kenya entered a new chapter with the swearing in of Mr. Kibaki, who heads a coalition of parties that up until last Friday's election had been long relegated to the opposition. All at once this afternoon, 39 years of domination by Mr. Moi's ruling party, the Kenya Africa National Union, came to an end. Advertisement

A former finance minister and vice president to Mr. Moi who broke with him a decade ago, Mr. Kibaki pledged to immediately launch his plans to revive the economy, to stamp out corruption and to rebuild government without any vestiges of the outgoing leader's autocratic rule.

"Fellow Kenyans, I am inheriting a country which has been badly ravaged by years of misrule and ineptitude," Mr. Kibaki said bluntly, with the outgoing president sitting expressionless nearby. "There has been a wide disconnect between the people and the government."

The retiring president, who has ruled Kenya since 1978 but was forced by the constitution to step down this year, ceded power graciously today in a ceremony few Kenyans ever imagined they would see. "

We have come a long way together," Mr. Moi said wistfully, as some in the crowd heckled him. "We have accomplished much, but there is much new to do."

Expectations for the new government could not be higher. Street children in rags joined smartly dressed business people today in dancing in the streets, hopeful that their lives would improve with a change at the top.

"I never thought I would see this day," said Mercy Gachiri, 42, who slept in Uhuru Park to get good view of the hand-over ceremony.

The hastily arranged inaugural drew some regional leaders, including the presidents of Tanzania, Uganda and Zambia. But it was everyday Kenyans who made the celebration their own.

They climbed into trees for a peek at their new president. They pushed and shoved their way past security personnel. When Mr. Kibaki arrived, they exploded into a frenzy that some said equaled the celebrations held at the time of independence in 1963.

"This is liberation," said Elvis Odoyo, 24, an accountant. "It's like gaining independence one more time."

The departing Mr. Moi, 78, was from the old-school of African politicians that demand absolute loyalty from the populace. For much of his tenure it was against the law to speak ill of him.

Mr. Kibaki, 71, comes from the same generation as Mr. Moi but he sounded a far different note today.

"I promise not to let you down," he said. "I will be your servant with all humility and gratitude."

Tackling corruption, Mr. Kibaki said, will be his immediate priority. He also plans to eliminate the fees charged to Kenyans who send their children to primary school, a costly promise but a hugely popular one. Most of all, Mr. Kibaki vowed to form a government with a different attitude than the outgoing one.

"The era of anything goes is now gone forever," Mr. Kibaki said. "Government will no longer be run on the whims of individuals."

Still to be worked out is how aggressively to go after past economic crimes. Mr. Kibaki has talked of a reconciliation commission to allow former officials to confess their misdeeds as well as a prosecutorial body to push forward cases that are ready for court. Today, he said he would not engage in any "witch hunting" but would not turn his back on the misdeeds of the past either.

The American ambassador, Johnnie Carson, said that if Mr. Kibaki launches a serious crackdown on corruption it would likely prompt international financial institutions to restart the aid to Kenya that has been frozen in recent years because of concerns over misspending in the Moi government.

"Something very dramatic has happened here in the last week," Mr. Carson said in an interview, calling the peaceful transition from Mr. Moi to Mr. Kibaki "strong affirmation that democracy can work in large African countries."

Kenya's step forward comes as other countries on the continent, such as Ivory Coast, find themselves losing progress. And democratic transitions like the one played out in Kenya remain pipe dreams in places like the Congo, Sudan, and Eritrea.

Still, the euphoria over Mr. Kibaki's victory belied the difficult road ahead for the new Kenyan leader. Mr. Kibaki's National Rainbow Coalition won 122 seats in the 210-seat parliament, enough to guarantee a majority. Yet even as they celebrated today voters said they felt more powerful before than ever before and would have no qualms about casting out Mr. Kibaki if he does not deliver.

"A cow that can no longer plow should be replaced," said Geoffrey Wambwa, 35, one of the many Kenyans who have graduated from university but still find themselves without a job.