Tran Khuong Dan, a construction foreman from Hanoi, was shocked when, in 1975, he finally saw his elder brother in Ho Chi Minh City (formerly Saigon) after a 21-year separation prolonged by the Vietnam War. Gaunt and pale, the brother displayed symptoms that were all too familiar to Dan. The brother, like their father, was addicted to opium. "All around me," says Dan, "there were drug addicts." The habit eventually led to his father's death in 1976 and his brother's the following year.

Despite their addiction, both men had practiced traditional herbal medicine and had prescribed remedies for thousands of patients. With the knowledge passed down from his father, Dan built himself a thriving practice in Ho Chi Minh City, eventually accumulating some $75,000. But one question continued to nag him about his brother's and father's deaths: "Why didn't they find a medicine to cure themselves?"

Dan then set out on a cross-Vietnam journey with a single goal: to find a cure for opium addiction. He collected more than 100 herbal potions that villagers substituted for opium when their poppy crops failed and their supplies dwindled. Eventually, he decided on a drastic step: to addict himself to opium and experiment on himself. "I knew from my brother how dangerous this could be," he says, "but I decided this was the only way."

He moved from village to village, smoking opium with tribal chieftains, then returned home and began boiling pots of water and herbs in his kitchen. He tried one herb combination after another, going cold turkey while seeking a remedy. His withdrawal symptoms were "like torture," he recalls, and time after time he went back to his opium pipe for relief.

After six months of self-experimentation, Dan says he finally found a concoction that enabled him to kick his habit, but to test it further he became addicted to heroin--and found his brew cured him of that as well. It was a muddy-brown syrup, later named Heantos, made from the leaves, roots and stems of 13 plants and a splash of alcohol. After he announced his breakthrough in 1989, Dan was immediately besieged by addicts. Since then, he says, some 4,000 patients have been treated, and most of them have been cured.

Now the U.N. is funding a study of Heantos' effectiveness , which will be overseen by the Johns Hopkins medical center. The brew will be analyzed at U.S. labs, and patients using it in Vietnam will be closely monitored. If Dan's elixir is proved effective, it may one day help the world's heroin addicts kick their deadly habit.

--Reported by Tim Larimer/Hanoi