Iran's new ultra-conservative President Mahmoud Ahmadinejad has been sworn in at a ceremony in parliament in Tehran.
The ex-Tehran mayor succeeds the pro-reform Mohammad Khatami, who held office for eight years.
Correspondents say that with the new president in office, hardliners now control all institutions of power and the reform period is over.
Mr Ahmadinejad takes power amid growing international opposition to Iran's decision to resume uranium conversion.
After his endorsement by Iran's supreme leader Ayatollah Ali Khamenei earlier this week, the new president said he would lobby for the elimination of weapons of mass destruction around the world and for international justice.
Before the July election, Mr Ahmadinejad - a former Revolutionary Guard - was little-known in the international arena. Although he did not start out as favourite, he won in a run-off by a big margin.