In what could put a decisive end to decades of bloodshed in Afghanistan, 351 leaders took oath on Monday as members of first popularly elected parliament on Monday, report agencies.
The national assembly opened after a reading from the Quran, the national anthem and a folksong by schoolgirls dressed in brightly colored robes.
Former warlords, ex-communists, Taliban defectors and women activists were then sworn-in despite threats by Taliban guerrillas.
However, there was some disappointment among sections of the gathering since many in those sworn-in are accused of serious rights abuses and links to the drugs trade.
President Hamid Karzai, while acknowledging the country's problems with poverty, corruption and terrorism, hailed the parliament as a symbol of unity and observed that this was a sign of Afghanistan regaining its honour.
"This homeland will exist for ever!" he added.
Karzai said there was a need for national reconciliation after almost three decades of warfare and called upon the Taliban to abandon insurgency, which has intensified in the past year despite his efforts to encourage defections.
United States Vice President Dick Cheney, who was among the guests at the ceremony, said it was a privilege to be present for the historic event.
Soon after the ceremony, Karzai said he was considering reshuffling his cabinet and cutting the number of ministries.
Sources said the President appeared to have enough support in parliament to avoid major problems, but could face difficulties with appointments, given the disappointment at his administration's failure to improve people's lives and carry out crucial reforms.