This is what vibrant religious life looks like in one corner of American Judaism:

• T-shirts that say “W.W.B.D.?” (What would Barbra do?) above a sketch of Streisand herself or “Yo Semite” (made in San Francisco).

• A man in drag teaching Torah.

• A Web site called Mazal Tov Cocktail, a self-described “encyclopedia of Jewish radical culture” represented by a flaming rag inside a bottle of Manischewitz.

A marriage of hip and Jewish that emerged in the late 1990s has redefined religious identity for twenty- and thirtysomethings from New York to Los Angeles and beyond.

They flock to all-night multimedia celebrations of Jewish holidays (like “Dawn,” held in San Francisco on Shavuot), fill nightclubs where Jewish storytellers are the headlining act and start magazines, journals and Web sites, all while wearing a wide array of irreverent clothing. Among the edgier items is a bra made out of yarmulkes.

Traditional Jewish leaders who for years have been wringing their hands over declining religious observance among young people and rising intermarriage rates are hardly rejoicing at the trend. For them, it is a superficial fad as welcome as a Chanukah bush.

“I’ve heard many off-the-cuff comments that are quite critical,” said Steven Bayme, an expert on contemporary Jewish life at the American Jewish Committee, the near century-old advocacy and social service group.

But the young thinkers spearheading these new ventures say their elders should look beneath the kitsch. There, they say, Jewish leaders will find the modern-day answer to the question that has vexed every generation including this one: how to keep the religion alive.

“Our mission is to promote Jewish literacy and to empower people to take it on their own terms,” said Amichai Lau-Lavie, 36, president of Storahtelling, whose shows are an explosion of traditional ritual and contemporary performance. He sometimes goes onstage dressed as a woman, Hadassah Gross, a Jewish motivational speaker and widow of six prominent rabbis whose motto is “a little bit of irreverence is very good for battling irrelevance.”

The significance of this debate within the community cannot be overstated. Jewish groups have spent millions of dollars researching how they can prevent young people from abandoning their faith, as studies have found they are doing in steadily increasing numbers. Community leaders have started outreach programs ranging from free Israel trips to singles dances to hip cafes — all aimed at trying to hang on to the younger generation.

But these efforts, while achieving some success, haven’t come close to the popularity of the outlets young people have devised for themselves. Storahtelling is booked around the country.

No one disputes that these events are attracting young people who previously had little or no contact with the Jewish community. However, traditional leaders say it is difficult to see what the happenings provide other than a good time.

Roger Bennett, 36, vice president at the Andrea and Charles Bronfman Philanthropies in New York and a leader in supporting innovative programs for young adults, contends the Web sites, clothing and performances are not an end in themselves. They are a “distribution point” for experiences that lead to deeper exploration of what it means to be Jewish, he says.

Bennett is co-founder of Reboot, a nonprofit aiming to recreate Jewish community through film, discussion salons, a quarterly journal and music. The music arm of Reboot has reissued the 1959 album “Bagels and Bongos,” a Latin-Jewish music recording by the Irving Fields Trio. Bennett is also a co-author of “Bar Mitzvah Disco,” a book of photos and essays about the coming-of-age rituals in the 1970s and ’80s.

“Jewish history is one of challenge and response. Its very strength is that it changes from generation to generation,” Bennett said. “It’s nothing to be afraid of.”