LEXINGTON, Mass. — Sundays at the evangelical Grace Chapel megachurch look like the American ideal of race relations: African-American, Haitian, white, Chinese and Korean families sing along with a white, guitar-playing pastor.

U.S. churches rarely have this kind of ethnic mix. But that's changing. Researchers who study race and religion say Grace Chapel is among a vanguard of megachurches that are breaking down racial barriers in American Christianity, altering the long-segregated landscape of Sunday worship.

"Megachurches as a whole are significantly better than other congregations at holding together multiracial, multiethnic congregations," said Scott Thumma, an expert on megachurches and a professor at Hartford Seminary in Connecticut. "It's absolutely clear."

A study by Thumma and the Leadership Network, a Dallas group that works with pioneering churches, found that minorities make up 20 percent or more of worshippers in nearly one-third of the nation's 1,200 megachurches. More than half of the megachurches say they are intentionally working to attract different ethnic groups, according to the 2005 study, part of a book that Thumma and network executive Dave Travis will publish in July.

The question now is whether the new diversity is just a fad or a permanent shift.

Although megachurches each draw at least 2,000 worshippers a week, they are a small percentage of the estimated 350,000 congregations across the United States. And leaders at Grace Chapel and other megachurches where whites remain the majority acknowledge enormous challenges in making minorities feel included so they'll stay for the long term.

Still, megachurches are trendsetters, and the change they've made is startling considering nearly all other American churches serve one ethnic group. Even churches with a large number of immigrants generally have separate English and non-English services. For black and white Christians, pre-Civil War church support for slavery and the general absence of white evangelicals from the civil-rights movement continue to drive the two groups apart.

Most megachurches don't carry that historical burden; nearly all have been built since the 1970s and play down any ties to a denomination.

But that's not the main attraction.

Researchers have found that whites and nonwhites join megachurches for the same reasons: great guitar-and-drum worship bands, strong programs for kids and a message of Bible-based self-betterment. For anyone who feels isolated in a sea of white faces, the small communal groups that megachurches form for their members provide support.

Oddly, megachurch pastors mostly discovered their crossover appeal by accident — despite a reputation for marketing savvy.