"The evidence suggests that a strong undercurrent of Jewish hatred persists in America," said Abraham Foxman, national director of the Anti-Defamation League, which released the survey Tuesday.
The survey didn't provide statistical data for the apparent rise in anti-Semitism, but Foxman said it could be linked to the Sept. 11 terrorist attacks and a belief that Americans were targeted because of the U.S. government's support for Israel.
"The American people are more unsettled, they're still wondering, 'Why do people hate us?' They're searching for answers," Foxman said.
When asked in other polls whether they sympathize more with Israel or the Palestinians, Americans consistently have said Israel by about a 4-to-1 margin throughout this year. But when the question is asked differently, a majority in other polls have said they would like the U.S. to take a neutral position in the conflict.
The ADL survey's findings are based on an "index of anti-Semitic beliefs" used by researchers in four previous surveys over the past 35 years. The survey measured bias by the number of affirmative answers to 11 questions, including, "Do you believe Jews have too much power in the United States?"
In 1992, the same survey found that 20 percent of Americans fell into the hardcore anti-Semitic category. That had fallen to 12 percent in 1998.
The new survey deemed 48 percent of the country prejudice-free, down from 53 percent in 1998.
"We are greatly concerned that many of the gains we had seen in building a tolerant and accepting America have not taken hold as firmly as we had hoped and have, to some degree, been reversed," Foxman said.
The national survey, conducted from April 26 through May 6, polled 1,000 Americans over age 18. It has a margin of error of plus or minus 3 percentage points.