John Kufuor was sworn in Sunday as Ghana's new president, succeeding longtime ruler Jerry Rawlings.
The incoming head of state swore "to be faithful and true to the Republic of Ghana" and to uphold the constitution.
"I dedicate myself to the service and wellbeing of the people of Ghana ... and to do right to all manner of persons," he said in the ceremony outside Parliament House in Accra.
From BBC
John Kufuor has been sworn in as Ghana's new president, succeeding the country's long-time ruler Jerry Rawlings. Leaders from across west Africa attended the ceremony in the capital, Accra.
The BBC's Barnaby Phillips says that, in a region where military coups and civil wars are so common, Sunday's handover gives an encouraging signal that peaceful democratic change is possible.
But he says the new government faces the difficult challenge of realising the promises it made during last month's election campaign - to improve social services whilst also pushing through tough economic reforms.
It was the first peaceful democratic transfer of power since Ghana's independence, and outgoing leader Jerry Rawlings, who was obliged under the constitution to stand down, has called on the army to show loyalty to Mr Kufuor.
The former opposition leader defeated the governing party candidate, Vice-President, John Atta Mills, in a run-off presidential ballot at the end of December.
Collective dignity
On Saturday, Mr Rawlings made his final address to the country's armed forces as their commander-in-chief, appearing before the troops in full military dress.
He told the troops he was leaving office with the same sense of optimism and hope that he had in 1981 when he mounted the second of two military coups that brought him to power.
Mr Rawlings said that under his leadership the people of Ghana had regained their collective dignity.
He said that he was not a fan of multi-party democracy, but he nevertheless took credit for fostering political awareness in the electorate.
Ambassadorial role
One of his last acts as president was to pardon an old political foe convicted of treason against his government in 1982.
Kwame Pianim, had served 10 years of a 20-year prison sentence.
Mr Rawlings is expected to take up UN Secretary-General Kofi Annan's invitation to become a roving ambassador to promote philanthropy in 2001.
"When this work takes me to other parts of the world, I hope I can point to Ghana as a prime example of the voluntary spirit," he said.
Correspondents say Mr Kufuor, known as the "Gentle Giant", lacks his predecessor's common touch and, despite his victory, still has a mountain to climb before establishing himself as leader of the Ghanaian people.