In Indonesia, they work on isolated fishing platforms, working heavy nets for long hours, often on very little food.
In Haiti, they face slavery and sexual servitude in households to which they are driven by poverty.
In Uganda, Sudan, and elsewhere, they serve as front-line soldiers, required to kill.
Under a new convention, adopted June 17 by the Geneva-based International Labor Organization (ILO), an arm of the United Nations, the "work" that falls to millions of the world's children will be banned.
The convention, which seeks to outlaw "the worst forms of child labor" - including slavery, sexual exploitation, and hazardous or heavy manual labor - also includes a ban on forcible military recruitment.
The gulf between adopting a well-meaning convention and really pulling the plug on abuses is vast. But there are some signs of progress.
It is a cause with momentum. A day earlier, President Clinton had called for the worst forms of child labor to be "wiped from the earth." And in the days after, the Group of Seven (G-7) richest nations pledged to help implement the ILO's call.
Save the Children, a London-based group that has campaigned for 15 years against child labor, largely welcomed the convention. But spokeswoman Rachel Marcus says: "It is important to make sure it is not just on paper but implemented as well."
The ILO, which groups trade unions, businesses, and governments, estimates that about 250 million children aged 5 to 14 are working in developing countries - half of those full time while the rest combine work and school. As many as 60 million of those are under 11.
THE number engaged in the "most abusive" forms is unclear but probably runs into the millions. Activists hope the attention will trickle down to all working children.
By some estimates, 300,000 to 1 million children are working illegally in the United States, most of them in agriculture.
Earlier this month, Mr. Clinton ordered US federal agencies to list products suspected of being made by forced child labor. He also required federal contractors to certify no abusive child labor went into goods they buy.
The administration has identified problem industries, including those making carpets and bricks in India and Pakistan, fireworks in Guatemala, and the use of fishing platforms in Indonesia.
Critics say Clinton should seek to make such protection part of free-trade agreements. Ms. Marcus of Save the Children and other children's-rights campaigners say the chief problem is implementation. There has been a general ILO convention on child labor for years, but many countries still have not ratified it. ILO officials say they have no illusions the new convention will be universally applied, but argue the ratification process is crucial for raising public awareness.
The group has bodies that monitor compliance with its conventions, but they have no disciplinary power over offending national governments.
"We should not underestimate the difficulties in getting ministries of labor to improve their inspection of workplaces, particularly in countries where resources are low," Marcus says.
Child labor has powered much of Indonesia's economy, for example - from the rubber plantations of Sulawesi to shoe factories on the main island of Java. Indonesia has yet to sign on to the new ILO convention.
President B.J. Habibie has indicated his willingness to ratify it, but development workers based in Indonesia say that may take some time. It's still too early to tell how well the ban on "ordinary" child labor, which Indonesia signed in May, will be enforced, let alone attempts to abolish hazardous jobs.
And Indonesia is still suffering from an economic crisis that has bumped millions back into poverty, an incentive for parents to have a child help fill the family coffers.
The government estimated last year that 2.1 million children were working, a figure one ILO official in Indonesia, Pandji Putranto, calls extremely conservative. He points out that some 6.5 million children have dropped out of elementary and junior high schools in the last year. Many are working as street vendors.
The ILO estimates more than 70 percent of Indonesia's child labor takes place in the agricultural sector. In October, the ILO is set to work with North Sumatra on one of Indonesia's most hazardous child-labor jobs - working on offshore fishing platforms.
"We have to ensure these children who have already been removed from these fishing platforms [in government sweeps] are not returned," says Mr. Putranto.
But the recession and local attitudes pose a challenge. "We have to be careful not to remove them from work without solutions," says Putranto, mentioning scholarships or economic incentives. But he notes that "most people think [fishing platform work] should be eliminated, but in areas like footwear, most people ask us, 'Why should we ban kids from work?' "
Putranto points out that since Mr. Habibie took power in May 1998, Indonesia has ratified conventions dealing with freedom of association, equal rights, and forced labor, becoming the only Asian nation to ratify all seven ILO conventions.
But he adds a warning. "It's easy to ratify," he says. "It's hard to comply."
Save the Children and other child-advocacy groups also express reservations about the fact that the convention does not ban outright the recruitment of under-18s for military service.
According to London-based rights group Amnesty International, some 300,000 children under 18 are currently fighting in conflicts worldwide.
The issue of child soldiers was highly controversial at the conference. Countries such as the United States and Britain both recruit people as young as 17 for the military. The final text took their concerns into account and only bans "forced" recruitment.
Other issues, like sexual abuse of children, are quicker to gain broad condemnation. Thousands of children are handed over by impoverished parents to families who can afford to raise them under Haiti's little-known Restavec system, literally "stay-with" in Creole.
"These Restavec children have no rights. They don't go to school but are made to do domestic work," says Eduardo Araujo, who works in Latin America for the ILO's International Program for the Elimination of Child Labor (IPEC). "They are often treated like slaves, sexually abused and beaten. But the problem is that it's almost an institution there. People don't always understand why it is wrong when you try to explain," says Mr. Araujo.
Araujo argues that while it is difficult to change ingrained practices, the convention is a good start. He says his organization, which runs programs in more than 60 countries to get children out of work and into school, has had some successes. In Central America, for example, the group has taken on the Peruvian mining industry, forcing it to withdraw children as young as 6 from the gold mines and help put them in schools.
Pakistan is an example of how international pressure - and praise - has had an impact. Clinton recently cited the country's case as just one example of the "work being done to eliminate child labor from the soccer-ball industry in Pakistan."
His words of encouragement followed a five-year effort by Pakistan that began when it first found itself the target of global concerns over the use of child labor in export-oriented industries like carpet weaving.
That criticism had triggered concerns among Pakistani exporters that their businesses would be hit hard if Western countries slapped restrictions on Pakistani goods on the grounds that they were made by children.
"That was a moment of great anxiety," recalls a leading Pakistani soccer-ball exporter, who requested anonymity. "We were charged into taking action when it became obvious that it was a matter of ... change for survival."
Clinton's recent remarks acknowledge the change in some 80 villages around the city of Sialkot in Punjab province. There, the manufacturing of soccer balls has been taken over by women. Exporters now use some profits to fund children's schools.
Critics say the battle to improve the conditions in one industry should not suggest that all is well for Pakistani children. But many acknowledge it's a start.
"The international dimension of the issue made our industry, especially that in Sialkot, very sensitive to the issue of child labor," says Salman Shah, a leading Pakistani economist.
"That sensitivity has led to the progress being talked about now," he says.
* Staff writer Nicole Gaouette in Jakarta and correspondent Farhan Bokhari in Islamabad contributed to this report.