Rima Adler had exchanged a couple of messages with a guy on JDate, but hadn't yet read his profile. When she finally did, she saw something she wasn't expecting he wasn't Jewish; it said so in capital letters.

The 34-year-old District resident quickly wrote back to tell the man that she wasn't interested in dating someone who wasn't Jewish, and he told her he understood.

Still, she was surprised. "I guess my assumption was that the reason to go there was because ... everybody [would] be Jewish," she said.

Increasingly, that's not necessarily the case at the Jewish online dating site.

A new book, Microtrends: The Small Forces Behind Tomorrow's Big Changes, by Mark Penn with Kinney Zalesne, who both live in the District, states "nearly 11 percent" of JDate's members are non-Jewish.

JDate spokesperson Gail Laguna would not confirm that number, but said that about 10 percent of the site's active members list themselves as "unaffiliated" under the category of religious background which likely included a significant, but undetermined number of non-Jews.

About two years ago, the site added a "willing to convert" option to the religious background question, according to Laguna. She would not reveal the number of people who listed that category on their profiles because, she said, any of the site's 350,000 active U.S. members who registered prior to November 2005 would not have had that choice.

The alternative was created because JDate officials realized that with non-Jews on the site, it needed to provide a "better option" for members to "communicate who they are," Laguna explained.

Penn best known as a pollster and strategist for presidential candidate Hillary Rodham Clinton and, before that, an adviser to her husband and Zalesne, a past executive vice president of Hillel: The Foundation for Jewish Campus Life, argue in their book that the surprising number of non-Jews on JDate is a manifestation of a "microtrend" of "pro-Semites," or non-Jews seeking out Jews as spouses.

Microtrends, according to the book, are "small, under-the-radar forces that can involve as little as 1 percent of the population but which are powerfully shaping our society."

In an interview, Penn said his research into "pro-Semites" was sparked by a poll he came across in which Jews were the "most admired religion" in America. That led to a survey conducted by Penn's firm in September 2006 that found that nearly four in 10 non-Jews said they would be "very" or "somewhat" interested in dating or marrying a person who is Jewish.

The book notes that "the number one reason they gave for desiring a Jewish spouse was a sense of strong values, with nearly a third also admitting they were drawn to money, looks or a sense that Jews 'treat their spouses better.' "

In an interview, Penn and Zalesne admitted they were surprised by their poll's findings that the segment of the population most interested in dating Jews consisted of "liberal to moderate, slightly downscale, Catholic men."

The authors speculate that the shared Catholic and Jewish emphasis on "family values" and "strong orientation around food" are driving forces.

Penn said the pro-Semite trend is one example of "increased tolerance" of racial, religious and class differences throughout society, adding that the pro-Semites are a "symbol of the lessening of intensity of anti-Semitism seen in the past."

This "pro-Semite" microtrend comes despite recent polls that consistently show a fear of anti-Semitism remains prominent among Jews. For instance, an American Jewish Committee survey last year found that 26 percent of American Jews thought anti-Semitism was a "very serious problem" in the U.S. and another 65 percent believed it was "somewhat of a problem."

Zalesne said that it's not surprising that Jews might have "more of a heightened sense" of anti-Semitism, and the AJCommittee poll numbers are a sign that "it can take some time for perceptions to catch up with reality" and that "old habits can be hard to break."

Current and former JDaters said that while they had no interest in meeting non-Jews on JDate, they generally didn't mind their presence on the site as long as they disclosed their religious background.

"It's a little weird," said Lisa of Germantown, who used the site for a year and did not want her last name published. "I'm not ... thrilled" by it, the 33-year-old said, because JDate is a "specific site for specific people."

With everyone using the site assumed to be Jewish, she views not telling a prospective date that one follows another religious faith is "withholding the truth" and akin to a married person using the site.

But, she added, if someone is "obviously upfront" about his non-Jewishness, "I guess it's OK."

Steve Mirman, 34, agrees.

"As long as you can see what you're getting into," said the Rockville resident, who used JDate off and on for a couple of years in his search for a Jewish mate.

Mirman said he had come across women on the site who said they were "willing to convert," but saw dating such a woman as "a bit of a gamble" because there was no guarantee she would fulfill such a promise.

Bethesda's Harry Chauss said that after seeing someone on the site who listed herself as "willing to convert," he e-mailed her out of curiosity to ask her politely why she was on the site. The woman responded that she was halfway through the conversion process.

Chauss, 37, said the presence of non-Jews on the site didn't really bother him. He said that he is drawn to profiles of women who say "something interesting" about their relationship with Judaism, so anyone who isn't Jewish wouldn't even register on his radar.

But Tamara Harris, also of Bethesda, said that with so many "other dating sites [where] people can go ... I think it would be nice if it was a strictly Jewish site. ... JDate should regulate it more."

Harris, 29, approved of the addition of the "willing to convert" option for religious background as a good way to help identify non-Jews on the site.

To Mirman, the presence of so many non-Jews on the site is "a compliment to some extent."

At the same time, he said, people who use JDate because they believe that Jews make good spouses may be guilty of ethnic stereotyping. He knows plenty of Jews who wouldn't fit that description.

Non-Jews aren't pursuing Jews solely online. Miriam Brodie of Reston, now married, said she had an encounter with non-Jews at a JDate-sponsored bowling party a few years ago.

Brodie said she and her friends suspected "right away" that their two bowling partners weren't Jewish based primarily on their names. When the woman broached the subject, the men openly admitted that they were not Jewish, but had come to the party because they were interested in meeting Jewish women.

One of Brodie's friends recalled that the guys said they liked the "Jewish look," including dark hair and dark eyes.

Brodie said she thought that was fine. "As long as they were upfront and honest," she said, people can "make [their] own decisions," although she personally wasn't interested in dating a non-Jewish man.

"It's the age we live in," said Brodie. "We have friends of all different backgrounds." Jews can't wall themselves off from those of other backgrounds, she added, nor does she think they should try.

Adler, though, wondered whether there was a possibility that the number of non-Jews could increase to such an extent that JDate would just become a place for the "general population."

JDate spokesperson Laguna isn't concerned, saying that JDate's success stems from its being a community for Jewish singles.

"We're clearly a site designed for Jewish singles," she said. "I don't think we can make that any clearer."