Fifty years after atomic bombs fell on Japan, people came to Washington from across the country to hope for world peace and to pray that no other city will suffer again the devastation of nuclear weapons.

About 100 opponents of nuclear weapons rallied yesterday in Lafayette Square, where they weaved peace signs and shouted for the dismantling of nuclear weapons and for an end to nuclear testing and power plants.

The protesters then marched to the Lincoln Memorial, where they floated a convoy of Japanese candle lanterns down the Reflecting Pool to pay homage to the "souls that were lost in the atomic bombings" of Hiroshima and Nagasaki. Similar commemorations were held in cities across the country.

"Follow the peace sign," shouted Tammi Coles, coordinator of Washington Peace Center, which helped organize the march. "No more Hiroshimas. No more Nagasakis."

David Hostetter, a member of the center, said, "We feel the bombings were a tragedy, and we are determined that the bombings like that should never happen again."

At 8:15 a.m. Japanese time, 50 years ago today, the United States dropped the first atomic bomb on Hiroshima. More than 200,000 people are believed to have died in the bombings of Hiroshima and Nagasaki.

Rose Mannara, 71, was a college student when she heard the news. She remembered the euphoria, but she said she didn't understand the moral implications of the bombs.

"They said this would end the kill ing," said Mannara, a retired librarian from Syracuse, N.Y. "This would allow our boys to come home. . . . They said it would end all wars, that it was the war to end all wars. That didn't happen."

Mannara held a sign protesting nuclear weapons.

"If you live by the bomb, you die by the bomb," she said. "If you live by the sword, you die by the sword. We shoot first and then we try to talk. I know there are hard feelings among people who say Pearl Harbor was a tragedy. But two wrongs don't make a right."

Alex Kuzuma, of the Children of Chernobyl Relief Fund, told the crowd: "Out of the ruins of Hiroshima and the wreckage of Chernobyl, humankind is still struggling to extract some meaning."

Michael O'Keefe, an actor on the TV show "Roseanne," was among the crowd. A Zen priest, he came to the rally to recite a prayer "to feed a meal of compassion to hungry spirits and send them back to the land of the deceased. . . . The idea is just to remember."

Judi Friedman, a peace activist and member of People's Action for Clean Energy, said she was concerned about nuclear waste, emissions from nuclear power plants and the potential for nuclear accidents.

Friedman recalled an older friend who told her what it was like to see the newsreels of the bombing.

"She said, Oh my God, the world will never be the same.' I remember having great sympathy at seeing people with skin hanging from them and the guilt scientists had who worked on the bombs," she said.

Nearby, on a park bench, sat Yaguchi Tetsuo, a World Bank employee who had moved to Arlington from Tokyo recently. He was in primary school when the bomb was dropped.

"It's a very sad experience," he said, "not only for the Japanese but for Americans. It should not have been used against civilians."