It's a popular notion that Islam is the world's fastest-growing religion, and Christianity is on the decline.
But it's not true, according to information that suggests both faiths are expanding worldwide, with Christianity on the rise in places like South America, Asia and especially Africa.
"It's not a dying religion. Christianity is a vital religion," according to the Rev. Cecil Murray, of the First AME Church of Los Angeles.
Christianity's supporters say news reports on the scandals in the Catholic Church, which recently led to the resignation of Boston's Bernard Cardinal Law, have painted an incomplete picture of the religion. They argue that in many developing countries, the Bible's word is actually booming.
The media has focused too much on problems within the religion, say some.
"They're much more interested in what's wrong with Christianity and not in where it's flourishing, and where it is vital," said Father Thomas Rausch, of Loyola Marymount University. "The third world, the Southern Hemisphere is mostly poor, and it's in these countries where Christianity is mushrooming."
The numbers cited by certain experts seem to support that argument. Christianity was rare at the turn of the century in Africa, but some say almost half of the continent -- as many as 360 million people -- now worships Jesus.
Rev. Murray sees those gains as the successful result of decades of missionary work across the continent. "I think it is strong in Africa because Christians went to Africa in the last 75 to 80 years," he said.
Specific figures on the number of religious adherents vary widely. There are, of course, sharp divisions among sects and denominations within both Islam and Christianity that make it much tougher to determine overall numbers.
A huge majority of the world's Muslims are Sunni, the dominant branch of the religion across most of the Arab world and in many non-Arab Muslim nations like Pakistan, Turkey and Indonesia. Shiites, the majority in Iran and an important minority in countries like Iraq, are much smaller in number but tend to be viewed as more fundamentalist and extremist by many Sunnis.
Christianity, meanwhile, is split along Catholic-Protestant lines. And while the Catholic Church is a tightly organized hierarchy, there are a wide variety of Protestant denominations that compete with both the Vatican and each other for adherents to their specific brand of Christianity.
But whatever the case, most experts agree Christianity does have the most believers. And recent reports estimate that by 2025, that gap will widen even further, making Christianity by far the world's largest religion.