MISSION VIEJO, Calif. � Sheik Yassir Fazaga regularly uses a standard American calendar to provide inspiration for his weekly Friday sermon.

Around Valentine�s Day this year, he talked about how the Koran endorses romantic love within certain ethical parameters. (As opposed to say, clerics in Saudi Arabia, who denounce the banned saint�s day as a Satanic ritual.)

On World AIDS Day, he criticized Muslims for making moral judgments about the disease rather than helping the afflicted, and on International Women�s Day he focused on domestic abuse.

�My main objective is to make Islam relevant,� said Sheik Fazaga, 34, who went to high school in Orange County, which includes Mission Viejo, and brings a certain American flair to his role as imam in the mosque here.

Prayer leaders, or imams, in the United States have long arrived from overseas, forced to negotiate a foreign culture along with their congregation. Older immigrants usually overlook the fact that it is an uneasy fit, particularly since imported sheiks rarely speak English. They welcome a flavor of home.

But as the first generation of American-born Muslims begins graduating from college in significant numbers, with a swelling tide behind them, some congregations are beginning to seek native imams who can talk about religious and social issues that seem relevant to young people, like dating and drugs. On an even more practical level, they want an imam who can advise them on day-to-day American matters like how to set up a 401(k) plan to funnel the charitable donations known as zakat, which Islam mandates.

�The problem is that you have a young generation whose own experience has nothing to do with where its parents came from,� said Hatem Bazian, a lecturer in the Near Eastern studies department at the University of California, Berkeley, who surveys Muslim communities.

But the underlying quandary is that American imams are hard to find, though there are a few nascent training programs. These days, many of the men leading prayers across the United States on any given Friday are volunteers, doctors or engineers who know a bit more about the Koran than everyone else. Scholars point out that one of the great strengths of Islam, particularly the Sunni version, is that there is no official hierarchy.

But this situation is fueling a debate about just how thoroughly an imam has to be schooled in Islamic jurisprudence and other religious matters before running a mosque.

The downside for Islam in America, some critics argue, is that those interpreting Islamic law often lack a command of the full scope of the traditions carried in the Koran and the hadith, the sayings of the prophet Muhammad considered sacred.

�I call it �hadith slinging,� � said Prof. Khaled Abou el Fadl, a specialist in Islamic law at the University of California, Los Angeles. �I throw a couple of hadiths at you, and you throw a couple of hadiths at me, and that is the way we do Islamic law,� he added. �It�s like any moron can do that.�

Experts say the problem is exacerbated because few immigrant parents want their children to become imams.

�Immigrant parents want their children to become doctors, engineers, computer scientists,� Dr. Bazian said. �If you suggested that they might want their kid to study to become an imam, they would hold a funeral procession.� Ultimately, in the absence of trained sheiks, good religion in many American mosques has come to be defined through rigid adherence to rituals, Professor Abou el Fadl said, adding, �It�s ritual that defines piety.�

The few imams born or at least raised in the United States who win over their congregations tend to be younger men who can play pickup basketball with the teenagers, but also have enough training in classical Arabic and Islamic jurisprudence that the older members accept their religious credentials.

Imam Ronald Smith Jr., 29, who runs the Islamic Center of Daytona Beach, Fla., converted to Islam at 14 to escape the violence in his African-American community in Atlantic City. As part of his training, he spent six years studying at the Islamic University in Medina, Saudi Arabia.

�Foreign imams, because of the culture in their countries, kind of stick to the mosque and the duties of the mosque without involving themselves much in the general community,� Imam Smith said. �The hip-hop culture is difficult to understand if you have never lived it.�

The foreign imams� idea of mosque outreach, Imam Smith said, is sponsoring an evening lecture series where everyone sits around for an hour and listens to a speech about being devout or maybe world politics, which teenagers find less than compelling.

Mosque leaders say the risk is that younger Muslims, already feeling under assault in the United States because of the faith�s checkered reputation, might choose one of two extremes. They either drift away from the faith entirely if they cannot find answers, or leave the mosque for a more radical fringe.

Here in Mission Viejo, Sheik Fazaga wears street clothes much of the time, but dons traditional robes to deliver the Friday sermon at the mosque, a building distinguishable from the surrounding strip malls and low-slung office buildings mostly by its airy exterior dome of metal filigree painted sea green. It was a practice he started 10 years ago when he first returned home and kind of fell into the imam�s job around age 24, because some members considered him too young for the position.

Born in the East African nation of Eritrea, he moved to the Arab world before coming to Mission Viejo at age 15. Drawn toward Islam by college students, he enrolled in the Institute for Islamic and Arabic Sciences in America, a Virginia campus of al-Imam Muhammad Ibn Saud Islamic University in Riyadh, Saudi Arabia. The United States government expelled much of the faculty in 2004 as part of the crackdown on extremist Islamic rhetoric.

The school was accused of being an American outpost of the puritanical Wahhabi sect, a label Sheik Fazaga rejects. But that might be one reason he has been stopped for questioning some 20 times � every time he returns home from abroad.

� �How come you don�t dress like an imam?�� that�s their favorite question,� he said with a wry grin.

Younger Muslims seek him out for guidance, he said, and the fact that he is studying for a master�s degree in psychological therapy helps. Teenagers have requested advice about being addicted to Internet pornography, he said, and about sexual orientation. He counsels adolescents � gay and straight � that sexual attraction is natural, but to act on it is wrong and that any addiction should be treated.

Previous imams would simply admonish the youths that something was a forbidden abomination, subject closed.

Gihan Zahran, 43, an Egyptian immigrant, remembers a previous Arab imam who even told a much perplexed teenager that wearing Nike shoes was �haram,� or forbidden in Arabic, without explaining why. Some Muslims consider this aloofness particularly ineffective in America, given that they are a minority faced by majority practices like drinking alcohol that clash with their faith and that teenagers confront daily.

Ms. Zahran�s sister Nermeen Zahran, 42, recently went on a pilgrimage to Mecca. She is a real estate agent, and has not veiled her hair at least partly because it might affect her livelihood in a conservative place like Orange County.

When she went on the hajj, as it is called in Arabic, a fellow pilgrim asked the Egyptian imam who accompanied them from Southern California his opinion of her not wearing the scarf afterward.

�He was so mad, so offended and said he couldn�t believe it could happen,� Nermeen Zahran recalled over a glass of orange juice in the neat condominium she shares with her sister. His basic reaction, she said, was that there was no point in seeking forgiveness for previous sins if one did not take the veil afterward.

Ms. Zahran has also consulted religious figures about periodic bouts of depression, but the usual response was that her faith lacked vigor.

Now she talks to Sheik Fazaga about it, she said. �He tries to solve the problems and doesn�t tell you that you have to accept that this is your life, this is what Allah gave you, and if you don�t then you are not a good Muslim.�

She wonders, in the end, whether a purer form of Islam will develop in the United States, with prayer leaders focused on the concerns of the community, rather than not treading on the toes of the government that supports them, as in much of the Arab world.

Mosques will probably continue to address the wishes of the immigrant population for another decade, but after that the tide will shift away from them, experts suggest.

�Islam in America is trying to create a new cultural matrix that can survive in the broader context of America,� said Prof. Sherman Jackson, who teaches Arabic and Islamic law at the University of Michigan. �It has to change for the religion to survive.�