Vice President Dick Cheney and his wife looked on as the assembly opened amid tight security. But concern remained that the legislature can be a constructive force: About half its 249 members are regional warlords, some are Westernized refugees and others are illiterate.
The assembly convened after a reading from the Muslim holy book, a folk song from schoolgirls dressed in brightly colored robes and the singing of the national anthem.
President Hamid Karzai acknowledged the country's problems with poverty, corruption and terrorism, but hailed the parliament as a symbol of unity.
"This is an important step toward democracy," he said. Karzai closed his speech by tearfully declaring that Afghanistan was "again standing on its feet, after decades of war and occupation."
Cheney and his wife, Lynne, sat in the front row, and the vice president signed a guest book afterward. "It's a privilege to be present on this historic day for the people of Afghanistan," he wrote.
Despite doubts about some of the new legislators, the fact that a parliament is sitting at all is a victory for a nation recovering from decades of ruinous warfare and the repressive Taliban regime.
Afghans voted for the lower house in September, and also elected provincial councils that then chose two-thirds of the 102-seat upper chamber. Karzai appointed the remaining 34.
"Today was a very good day," said Kubra Mustafawi, one of the new assembly's women. Nearly one-third of the delegates are women. "After 30 years, the Afghan nation has gathered under the umbrella of peace."
Most of the government's power is still concentrated in the hands of the president, although parliament will be able to pass laws and veto Cabinet selections.
The country has had no elected national assembly since 1973, when coups and a Soviet invasion plunged it into decades of chaos that left more than 1 million people dead.
The Taliban's disastrous rule ended in late 2001, when it was deposed by the U.S.-led invasion for sheltering Osama bin Laden.