Uganda's President Yoweri Museveni has renewed his oath of office, following his re-election in February.
President Museveni was cleared of breaking electoral laws
Thousands of cheering people and 11 African heads of state attended the ceremony in the capital, Kampala.
Mr Museveni's leading opponent, Kizza Besigye, has alleged that the poll was rigged, and the main opposition boycotted the inauguration.
There has been international disquiet that the constitution was changed to allow Mr Museveni run for a third term.
BBC East Africa correspondent Adam Mynott says President Museveni won a convincing, if controversial, victory 12 weeks ago.
Thousands of Ugandans gathered at Kampala's Kololo independence square for the ceremony, which was also attended by diplomats and foreign dignitaries.
African leaders, including Thabo Mbeki of South Africa, witnessed President Museveni being sworn in once more.
Dr Besigye said he had been cheated of victory
In a 15-minute speech broadcast on national radio, President Museveni called for an end to the security problems in neighbouring Democratic Republic of Congo's security problems, which he blamed on "terrorists and negative forces".
"Some of these issues are not as difficult to resolve as they appear," he said.
Dr Besigye was charged with both treason and rape in the run-up to the polls, which he says was an attempt to either remove or at least distract him from the campaign.
He has been cleared of rape, while his treason trial is on-going.
Last month, the Supreme Court ruled by a four-three majority that there was no evidence that the results had been substantially affected by irregularities.
The judges found there had been problems but not enough to challenge President Yoweri Museveni's victory.
In addition to the pomp and circumstance of a state occasion, the gathering offered the opportunity for regional issues to be raised.
President Paul Kagame of neighbouring Rwanda was expected to take the opportunity to meet Mr Museveni to try to build bridges between the two countries, which have fallen out over allegations that Uganda has been supporting rebel activity in Rwanda.