At any moment of the day or night, Katie Vigil knows exactly how many days, hours, minutes and seconds it will be until Jason Thurgood returns from his LDS Church mission to Oslo, Norway. She simply glances at the "countdown clock" sitting on a desk in her dorm room.

The 19-year-old Brigham Young University student has several little aids to help her heart grow fonder in his absence: what Vigil jokingly calls "the shrine," which displays dozens of framed photographs of him or the two together, and the little diamond "promise ring" she wears on her left hand.

The freshman from Albuquerque has written every week to Thurgood, the boy next door she has dated since she was 15. She has sent periodic care packages and worked to stay close to his family. Each night before she goes to bed, Vigil affixes a heart-shaped sticker to the calendar charting his remaining days. "I imagine we will be engaged pretty soon after he gets home," she says.

Vigil's "waiting, not dating" approach is an extreme example of what thousands of other Mormon girls are doing while their beloveds serve two-year missions for The Church of Jesus Christ of Latter- day Saints. The church has a continuously replenished missionary force of 60,000, most of whom are 19-year-old men.

At a point in life when other young men are well into college or jobs, the Mormon youth put everything on hold to serve God. One curious measure of the impact: most Utah colleges are nearly emptied of men of that age. At BYU, there are 6,000 19-to-20-year-old women for their 300 male counterparts.

Thus has the Mormon missionary system -- which allows telephone calls home only on Christmas and Mother's Day and e-mails no more than once a week -- spawned a bevy of letter-writing romances with their own internal rules and rituals. Dear John letters. Missionary folklore. Statistics about marriage outcomes. Advice about the best mail system. And a whole industry of kitsch for the waiters, including key chains with slogans like, "I Love My Missionary" or "I Belong to Elder X."

> It is a phenomenon whose nearest parallel is found in wars of long ago, when thousands of American men left their lovers and wives behind to fight in foreign lands.

Just as love begins to bloom and young Mormon couples feel the stirrings of physical attraction, the men are whisked off to parts unknown, embarking on a disciplined, supervised spiritual journey that the girls left behind experience only vicariously. Sexual abstinence is expected of all parties. (Now that more young women serve their own 18-month missions, there is a small group of young men waiting in the wings.)

The vast majority of couples agree to write, but take a "wait- and-see" view, making no commitments about the future. "It's a period of life where people change and grow and develop so much," says Carmen Pingree of Salt Lake, who served as the "mission mother" to hundreds of young men and women while her husband, John Pingree, was a mission president in Mexico City from 1998 to 2001. "Sometimes they grow in the same direction and sometimes they don't."

There is nothing wrong with waiting for someone and nothing wrong with not waiting, Pingree says. "People just need to keep their options open."

Rituals of Waiting

Not long after the first letters are exchanged, many girls experience a letdown. The missionary's missives inevitably become less personal and more focused on the task at hand. The transition from "mushy" warblings of starry-eyed lovers to impersonal letters about the mission experience can be tough.

"Before he left I was one of his biggest priorities," says Amy of Salt Lake City, whose boyfriend is in Argentina. "Now he is focusing on his missionary work. He was not especially spiritual before. Now he is totally on fire." "I wouldn't want it any other way," says Amy, "but it's still sad."

Similarly, the tone of Thurgood's letters became more distant, "less romantic and emotional," Vigil says. She responded by trying to match his style. "I wanted to keep from being a distraction," she says. "I understand and he understands that he is there to serve with his whole heart and mind. This is a small sacrifice to make to have him forever when he gets home."

Letter-writing can enhance or destroy a relationship. And it can have a powerful effect on the missionary's ability to function in the system. "It depends on the quality of the communication. If they are talking about ideas and issues, sometimes they get to know each other better that way," says Pingree. If letter-writers are "distracting and not on a mature level, it makes it difficult for the missionary, but if they are encouraging and helpful, they can be a serious source of support."

Gwen Bruner wrote to a missionary for the full two years, but when he got home, the relationship didn't work. But she doesn't regret it at all. "It was nice to know that someone far away supports you," says Bruner, of Salt Lake City. "For me, it was a good experience all around. I think it was the same for him."

The missionary ended up marrying her best friend and she was the maid of honor. Just writing to missionaries makes many young Mormon women members of a sort of club with its own particular patterns and rituals.