In rags and bare feet, they walk through Sao Paulo's dilapidated city center like ghosts.
Some beg for change that goes straight to purchasing the drug that has wasted away their bodies as surely as it has their personalities, their futures and their sense of self-worth.
They eat rarely and sleep where they can, usually to substitute unconsciousness for the wide-awake craving that consumes their lives.
This part of town is now nicknamed "Crackolandia", a theme-park connotation that is a grimly ironic take on the reality: a place where crack cocaine addicts have been congregating for the past seven years to smoke their drug.
It's a scene repeated in several Latin American cities which are struggling with a growing number of addicts drawn to the cocaine derivative that promises a 10-minute surge of dopamine-driven euphoria. Followed by a long period of irritability and even psychosis.
During the working week, the "crackheads" mill around a public square in front of the city's neo-Gothic cathedral, as suit-clad businessmen walk by. On weekends, when the area is deserted, they throw their mattresses on the ground, adding to the depressingly rundown scene.
"I smoke and I drink all day long," laughed Jean Janzy, one addict woken by a municipal social worker.
At 18 and looking fragile, Janzy is beyond caring where he sleeps.
"I'm used to sleeping in the street," he said. He explained that his begging rakes in 100 dollars a day, which goes exclusively to paying for crack.
He refuses the social worker's offers to help, or urging to take a bath. But he does give the name of his mother, whom he'd "like to see".
Wagner Abril Souto, a psychologist at the Cratod addicts' assistance center in the city, told AFP that crack's relative cheapness "quickly creates a dependency, and the effects on health are devastating."
The yearning to repeat the fleeting high pushes users "to want to take a hit again right away, which builds dependency."
Carlos Alberto da Silva, a 50-year-old homeless man who watched his shelter under a bridge fill up with addicts and their suppliers, said: "There are many who die in the street.... Nobody helps them."
Sandro Ribeiro, 22, said his habit caused his girlfriend to leave him. He is early enough into his addiction that he still holds on to hope.
"I want to get out of this situation, get papers and enough to eat," he told the social workers.
But many others have given themselves over to their meager existence that revolves around inhaling the off-white crystals.
"Crack makes them aggressive and it's difficult to approach them," one of the social workers, Andrei Chikhane Massan, 24, said.
One pregnant woman in Crackolandia rose from the ground when she saw an AFP photographer approach and threw insults and rocks at him until he moved back.
Her child, if she brings it to term, will probably suffer serious respiratory problems and an addiction as well, said another psychologist, Fernanda Haedo, of the Manantiales Foundation.
The efforts by the municipality are painstaking, and with little prospect of eradicating the ill.
The federal government is making a contribution to tackling the scourge.
Brazilian Health Minister Jose Temporao announced in October that 64 million dollars would be spent by the end of the year to provide care for crack addicts across the country.
"It's a serious problem that affects Brazilian society and we have to address it. It's a complex problem because it's ties to drug trafficking and crime," he said.