They are conspicuous for their clean-cut looks, neat uniforms of black suit, white shirt and highly polished shoes, and their book in hand. As they walk along the street, two abreast, passers-by avoid eye contact, burrow their heads in jacket lapels and are quick with a rehearsed brush-off.
The rebuffs are shrugged off by these followers of the Church of Jesus Christ of Latter-day Saints, or Mormons as they're known.
Committed to their mission to reach out to the unchurched, they've heard all your excuses before: the rejections, the abuse, the door slams and the people who hear their knocks but refuse to face them.
"I try to look people in the eye and shake their hands, but earphones are a killer, so are sunglasses," a missionary elder, Silas Pollard, tells the Herald as he joins his partner, Hsien Lu, in a walk of Sydney's Chinatown. Most missionaries wear out two pairs of shoe soles during their service.
On George Street, Pollard bumps into Taylor, an American visitor to Sydney, who boasts of Mormon friends and of having read the Book of Mormon.
"I also have the Koran and Chairman Mao's Little Red Book. You should get out and read more books," Taylor tells Pollard.
It's a rule learnt in missionary training that they not engage people in argument or debate. Pollard extends a hand, says he respects Taylor's opinions and the two leave on friendly terms without changing each other's minds.
Brisbane-born Pollard's approach is more laid-back, less insistent than that of Lu, an earnest 27-year-old convert from Taiwan who wears his faith with a greater sense of urgency.
Fresh-faced and gangly limbed, Pollard is 19 and on his first big trip from home. Put him in boardshorts and he could be any one of the teenagers milling around the city's movie precinct he passes on his daily route.
He doesn't like to push: "You can't teach people who don't want to be taught," he says. But does he ever get dispirited? "Only when people are nasty."
In Australia, where faith is considered a private affair, the Mormon church is growing, not atrophying like some of the mainstream Christian denominations.
Indeed, the church promotes itself as one of the world's fastest-growing religions, claiming 116,000 members in Australia - far more than official census data - and 12 million worldwide.
Utah is its home state, the Osmonds with their blinding smiles are its famous poster children, and its belief that salvation can be granted to dead ancestors lies behind its unique gathering of world genealogical records.
"There has been substantial growth in the church worldwide and in Australia and it's not to be dismissed," says Gary Bouma, professor of sociology at Monash University and a specialist in Australian religious diversity. Even allowing for conservative attendance data collected by the census, Bouma says between 1996 and 2001 the church grew by 11 per cent, on top of previous growth.
"It is now nearly 0.3 per cent of the Australian population, which makes it about the same numerical size as the Churches of Christ or the Salvation Army," he says. "And it's larger than the Seventh Day Adventist Church and it's growing while most other Christian groups are declining.
"Where is it headed in Australia? Straight for the mainstream."
The church does not have a priesthood, but it does boast a reservoir of young men and women willing to pay their way to spread the Book of Mormon.
Pollard and Lu are two of 809 missionaries serving in Sydney. It is a position of prestige in the church and one of personal sacrifice. Each paid the equivalent of $15,000 to cover air fares, missionary training - Pollard flew to Utah to learn Japanese, for example - uniforms and accommodation.
In turn, they receive a stipend of $131 a fortnight, which takes care of food and toiletries and not much else. Membership of the Mormon church demands sexual abstinence until marriage, obedience to the church and no coffee, alcohol and tobacco.
Their two years of missionary service - a kind of tithing on their time - also demands singular focus on faith to the exclusion of all things, even family. They couldn't tell you the latest movies and probably wouldn't know the latest news from the Middle East.
These young men (women can also be missionaries, but for men it's more expected) cannot watch movies or read a newspaper. Communication with immediate family is restricted: letters only, and two phone calls home a year on Mother's Day and Christmas.
Lu's term is almost at an end, having knocked on virtually every door in Hurstville and walked most of the streets of Rockdale, Kogarah and Penshurst.
Such dedication is illustrative of what a Queensland academic, Queensland University associate professor Richard Hutch, describes as the religion's "super-protestant" work ethic.
"Mormons deny most short-term personal gratification for some future glory and this is their lifestyle," he says. "You might say they are super-protestant; they are just carrying the protestant work ethic to the max."
The missionary experience does more than spread the word, it helps promotes staunch bonds of loyalty that characterises church membership. It lies at the very centre of the church's tradition of volunteerism and active lay leadership.
With the possible exception of the Amish, says Terryl Givens, an American academic scholar and a committed Mormon, no other American religion has been so successful in welding its members together into such a cohesive unit.
To its critics, however, Mormonism is an esoteric new religion built on the fantastical mythology of a founder, Joseph Smith, who unearthed and transcribed relevatory gold tablets and then proclaimed his church to be a true restoration of the church of the apostles.
The church is still trying to live down controversies such as polygamy, which was once encouraged but has since been outlawed.
And the emergence recently of the popular Republican Governor of Massachusetts, Mitt Romney, a Mormon, as a potential presidential nominee has highlighted tensions between Mormons and evangelical Christians.
Many evangelicals believe that Mormon theology - their beliefs on the nature of God, salvation and scripture and reverence of a modern prophet as head of the church - is incompatible with Christianity. Where Mormons believe in Jesus Christ and consider the Bible Holy Scripture, the church, evangelicals say, has substantial differences in belief from the Catholic and Protestant that go well beyond the fact that Mormons don't badge their churches with the Holy Cross.
Hutch disagrees with the assessment that Mormons aren't Christians, describing evangelical Christians and Mormons as "like distant country cousins". In the US, both Christian traditions, he says, are "slugging it out for political and economic influence", with the Mormon church - backed by its amassed finances - the more moderating force.
Theological wrangling is all academic for Akie Nakai, a Japanese working student, who converted five months ago and is instructed by Pollard and Lu. "I think it's good for husband and kids because I come from Japan and on Sunday husbands usually are working. In Japan it's work, work, work and you feel like you are dying for work," she says.
Lu knows first hand the impact of missionary work. He was converted at 18 by Mormon missionaries he met at a bookstore. It was his first contact with Christianity. His mother was Buddhist and until then he didn't know the Bible. What he found in the Mormon church was spiritual structure.
For Pollard, whose parents were converts, it's all he has ever known.
Despite the perils of cold calling, the two missionaries give out maybe a dozen brochures during this day, mainly advertising English-language classes, and receive one contact number.
Bouma says: "They wouldn't have a 100 per cent strike rate but if you are going to hit the doorstep, people are more likely to give an ear to someone who is fresh-faced, young and rather earnest than someone who is 48 and whiskered and representing groups they've heard from before."
Missionary work is as much about character formation as service to the church, the Australian church's president, says David Stone. He says rejection is a big part of a missionary's day, which is why the church is more discerning in whom they send these days.
Once they return home, Mormon missionaries tend to quickly marry and raise families. Lu and Pollard both have girlfriends waiting for them. They exude all the anticipation of a religious vocation half started and the innocence of a life barely begun.
"It's not as if people should feel sorry for us," Pollard says. "We don't have to worry about much except eating and studying. It's a personal calling. If we help anyone it is ourselves."