Wars, famine, genocide, torture, mutilation, abuse of women and children -- the bewildering array of human rights catastrophes around the world is enough to stymie any neophyte Samaritan. What crisis has the best claim on your money and time? Ethnic violence in Central Europe, repression in East Timor, or some other outrage you haven't even heard about yet? Increasingly, humanitarian groups in the West are focusing on a problem so alarming in its assault on human dignity that it easily trumps them all: slavery.

The word itself seems dated, plucked from a murky, unenlightened past when people somehow didn't understand that what they were doing was wrong. But slavery isn't merely a historical phenomenon, according to a growing consensus of activists and researchers around the world. It's a grim reality faced by as many as tens of millions of people on virtually every continent.

"If you get a huge increase in the population and a lot of people are being pushed into economic vulnerability, both of which have happened in the Third World, you've got lots of people who are very poor and easily manipulated," says Kevin Bales, a lecturer at the Roehampton Institute in Surrey, England, and author of Disposable People: New Slavery in the Global Economy. "The police don't protect them and you can enslave them. That's exactly what's happening in India and Pakistan and Thailand and Brazil and a lot of places around the world."

The most publicized case of slavery in the modern world is, according to many, not even the most extreme. The kidnapping of Dinka tribespeople by government-backed militias in the Sudan has captured headlines recently, but reports of Sudanese militias selling helpless villagers into slavery have been circulating for over a decade. Until lately they seemed less than urgent to researchers familiar with other crises besetting that region.

"Slavery is not the greatest problem in the Sudan by far," says Jemera Rone, a researcher with Human Rights Watch who focuses on the country. "Almost two million people have died in the course of the current civil war. One expert was saying it was probably 50,000 at the most [who had been enslaved]. Unfortunately, 50,000 is not a lot of people to have been affected."

It took an unorthodox effort by Christian anti-slavery organizations to catapult the Sudan's human rights situation into the public eye. Groups such as Christian Solidarity International Inc. and The American Anti-Slavery Group Inc. have recently begun sending representatives to Africa to purchase slaves and free them. The tactic is known, not coincidentally, as "redemption." Redemption capitalizes brilliantly on the economic disparity between the First and Third Worlds: In the impoverished Sudan, a human life is worth only around $50, a comparatively modest sum for Western do-gooders to raise. But the fact that the money goes into the pockets of the slaveholders has given many human rights experts, including Rone, pause. "It's worrying because it has the potential to attract more raiding and more profiteering by the raiders," she says.

That hasn't deterred activists like American Anti-Slavery Group representative Jesse Sage. "I know it's controversial, but this isn't a market with supply and demand," he points out. "The taking of women and children is merely a byproduct of a military situation." He adds that reports of kidnappings have actually gone down in the last year, so his group's efforts are hardly creating a market.

Besides, the prospect of buying a person's freedom is irresistibly seductive to Americans weary of the Sisyphean struggle to rehabilitate the Third World. Would-be freedom riders sent to the Sudan by Christian Solidarity International Inc. have returned with blithe idealism comfortably intact. One Colorado schoolteacher told newspapers how thrilled she was to see a recently freed woman suddenly give birth under a tree. "What can you say when you free a woman and you know that this child was born in freedom?" she said. "She can say that she was born free."

Such dubious victories are no consolation to activists who say millions around the world remain enslaved. The London-based group Anti-Slavery International estimates that about 30 million people may be living in bondage. "There are more slaves alive today than all the people stolen from Africa in the time of the transatlantic slave trade," Bales says. He uses the term to include bonded laborers in India, migrant workers imprisoned on plantations in Brazil, and slaves bound through generations of service to ruling families in Mauritania. Slavery may be technically illegal in these countries, Bales says, but the fact of compulsory servitude remains. "If people are paid absolutely nothing and they're held under a threat of violence and they're economically exploited, then they're in slavery," he says.

Bales says de facto slaves can even be found in London and Paris. Disposable People commences with an account of a North African woman who as a child was taken to France by a family who said they would send her to school in exchange for her labor. Instead she spent years being routinely abused and kept cut off from the world at large. "Although she was 22 and intelligent, her understanding of the world was less developed than the average five-year-old's," Bales says. "She had little understanding of time -- there was only the endless round of work and sleep. She is baffled by the idea of 'choice.'"

Bales adds that it's not necessary to remove people from their country of origin in order to deny them their rights. Anti-Slavery International is currently campaigning against debt bondage in India. Though it's against the law, the group estimates that more than 10 million people remain bonded laborers -- a situation that, Bales says, is the equivalent of enslavement.

"A lot of people misunderstand debt bondage to mean that somebody borrows some money and then they work as a way of repaying the money. But that's not the way it works," he says. "Your work doesn't repay the money. You and your work are just the collateral. The person you borrow from basically owns you and all your work until you repay them."

The complex economic and social realities of such a situation bear little resemblance to the $50 redemption promised by Christian Solidarity Inc. Unfortunately, the bondage endured by these de facto slaves may persist beyond their cheaply bought freedom.

Etelka Lehoczky writes regularly for Salon and the Chicago Tribune.