Almost every 19-year-old in the Church of Jesus Christ of Latter-Day Saints (LDS) goes through what one might call executive training camp.

It's an extremely rigorous two-year program: 10-hour days, no TV, no dating, constant rejection. At the same time many American teenagers are relishing their first taste of freedom as college freshmen, these Mormons are entering into the most disciplined period of their lives.

About 55,000 Mormons are dispersed around the world at any given moment, Book of Mormon in hand, preaching the gospel.

"I don't think there's any more demanding profession than being a Mormon missionary," Harvard Business School professor (and Mormon) Clayton Christenson tells Businessweek.

It's no surprise that Mormons rank in the high echelons of business. They're execs for major corporations like Marriott International, Dell, Deloitte, PriceWaterhouse Coopers, for starters -- and there's JetBlue founder David Neeleman, Credit Suisse CEO Eric Varvel, and Gary Crittenden, former CFO for Citigroup and American Express.

Two leading Republican presidential candidates have also come out of the LDS church: Mitt Romney, former CEO of Bain & Company, and Jon Huntsman, former ambassador to China.

In its excellent profile of successful Mormon leaders, Businessweek asked Gary Cornia, the dean of the Mormon-run Brigham Young University's Marriott School of Management, why this religious sect has churned out so many CEOs.

"I'm not going to say we beat everybody out, but we do have a reputation," he says. "And one of the defining opportunities for young men and young women is the mission experience."