As a youth, Moser left Austria to escape the Nazis; he joined the Hopkins faculty in 1976. Now 78 and the director of the Neurogenetics Research Center at Hopkins' Kennedy Krieger Institute in Baltimore, he has been trying to unravel and defeat ALD for more than 40 years.

''He's really still obsessed with the idea to come up with a treatment for ALD before his time is finished,'' Wanders says.

Moser's decade-long study, funded partly by the U.S. Food and Drug Administration (news - web sites), involved 105 U.S. and European boys known to have inherited the ALD gene. Symptoms usually don't appear until between the ages of 4 and 10.

The boys who entered Moser's study were 18 months to 6 years old and had normal neurological examinations and brain MRIs.

To his surprise, Moser found that the boys who stuck to a strict regimen of daily doses of Lorenzo's Oil and a very low-fat diet were, in a two- to four-year follow-up, a third as likely to develop brain abnormalities as the boys who did not adhere to the regimen.

Without mass screening, most boys with ALD would not be diagnosed until symptoms appear -- too late for treatment with Lorenzo's Oil or for a bone marrow transplant, another therapy that has had some success.

Neo Gen Screening, a company in Pittsburgh, received a National Institutes of Health (news - web sites) grant in August to iron out the details of its screening test, which it hopes to begin offering parents within the next six months. Because newborns have never before been screened for ALD, company President Edwin Naylor can only estimate that the disease is about as common in boys as phenylketonuria, or PKU.

All states require that newborns be screened for PKU, leading to the identification and care of several hundred affected babies each year.

Lorenzo cannot see or move

Sadly, none of these developments will benefit the young man whose parents' love led to the invention of Lorenzo's Oil. Lorenzo Odone was not diagnosed until he began acting out of character, moving awkwardly and losing his hearing. He wasn't quite 7 years old.

Now 24, Lorenzo has survived years longer than doctors had predicted. He has outlived his mother, Michaela, portrayed by Sarandon in the film. She died of lung cancer in 2000. Augusto Odone, played by Nolte, attributes his son's longevity to the eponymous oil he continues to take. That is more a father's conviction than a scientifically proven fact.

Lorenzo survives, but he cannot see, talk or move. His father cares for him at their suburban Virginia home with the help of nurses and Oumouri Hassane, a young man the family befriended when they lived in the Comoros Islands off East Africa. At the time, Odone, an economist, worked for the World Bank (news - web sites), and Lorenzo was an extremely bright child who could speak several languages.

One need only meet Ramon and Maritza Casso's sons to understand the potential of Lorenzo's Oil.

For the first eight years of his life, Juan Casso was a healthy, normal child. Then one day he went blind. Soon, he could no longer walk. Finally, he stopped talking. The relentless decline happened in a matter of months.

His frantic parents sought answers from top research centers. At Johns Hopkins, they learned the awful truth: Juan had inherited ALD, and there was nothing they could do to stop it.

As soon as Juan was diagnosed, his 6-month-old brother's blood was checked for high levels of VLCFAs, the very long chain of fatty acids that signal the presence of ALD. The Cassos were devastated to learn that they had twice lost the genetic coin toss: Baby Jose also had inherited ALD.

''Oh, my God, my two children will be the same,'' their mother recalls thinking. ''One in one bed, the other in another bed.''

Today, the brothers share a bedroom in their family's tidy third-floor walkup apartment in Washington's Adams Morgan neighborhood. But the contrast between the two boys is sharp.

Jose will turn 9 next month. By that age, Juan, now 16, was blind, mute and bedridden, getting nourishment through a tube in his stomach. Jose, on the other hand, is a bright, active fourth-grader. He's a computer whiz, speaks English and Spanish fluently and hopes to find a cure for his brother someday. Oh, and to be an astronaut.

There is no doubt in the Cassos' minds that the Odones' discovery has saved Jose from his brother's fate. Juan took Lorenzo's Oil after he was diagnosed but stopped when he continued to deteriorate. Jose began taking the pale yellow concoction when he was 18 months old. That's the earliest experts feel it is safe to do so. In addition, he follows the low-fat diet that goes hand in hand with Lorenzo's Oil.

Jose likes chicken with rice and beans and doesn't miss the pizza and hamburgers he's never had. When asked how Lorenzo's Oil tastes, Jose screws up his face and exclaims, ''Bad!'' But he faithfully gulps 5 teaspoons of it every day. If he doesn't, his parents have warned, he'll end up like Juan.

Moser is not so sure. He thinks there's no compelling reason to keep boys on Lorenzo's Oil and the special diet indefinitely. If, like Jose, a boy has a normal MRI at age 7, it's highly unlikely he'll develop the form of ALD that manifests itself in childhood, Moser's research has found.

Studies have not shown a benefit from Lorenzo's Oil in boys older than 10 or 11, Moser says, and it's unrealistic to ask a teenager to stick with such a restrictive diet.

The adult form

Moser is the first to acknowledge that Lorenzo's Oil is not a cure. The treatment is highly effective at lowering blood levels of very long chain fatty acids, or VLCFAs, which accumulate in the brains of boys with ALD, but it can't cross the blood/brain barrier.

Unless researchers can find a treatment that prevents the accumulation of VLCFAs in the brain, Moser says, boys taking Lorenzo's Oil eventually will go on to develop the adult form of ALD.

''The adult disease is mild compared to the childhood disease, but it's a very bad disease,'' he says. Still, Moser counts a judge, a CEO and a psychiatrist among affected adults.

Moser's and Wanders' labs are studying another promising compound, called 4-phenylbutyrate, which at least temporarily lowers brain levels of VLCFAs in the mouse version of ALD. They have not yet tested it in patients.

But what of Lorenzo and Juan and other ALD patients in whom the damage already has been done? In ALD, the accumulation of fatty acids strips nerves of their protective sheath, called myelin. Without myelin, impulses cannot travel from one part of the body to another. Besides rare inherited disorders such as ALD, acquired diseases such as multiple sclerosis can destroy myelin.

Toward the goal of restoring even a fraction of what his son has lost, Odone founded the Myelin Project to support cutting-edge research into regrowing myelin. So Odone, at 69 ever the charming Italian, is still raising money and prodding scientists, although his only doctorate is an honorary one.

''We are pioneers,'' says Odone, who is president of the Myelin Project. ''We want to put in some seed money. Then we'd like other, bigger organizations to take over.''

With a grant from the Virginia-based Myelin Project, scientists at Yale University have transplanted myelin-producing cells into the brains of three patients with advanced multiple sclerosis.

A biopsy of the first patient, transplanted in July 2001, failed to find signs of the cells, but Odone is not discouraged. That patient received only 1 million cells, a relative pittance, he explains.

Any day, Odone says, he expects to learn the biopsy results from the second patient, who received 5 million cells in March. Even if none of those took, Odone says, the two attempts at least showed that the procedure is safe. And that, he says, would spur at least one other institution to consider trying it.

''It's like a long shot, but it's better a long shot than no shot at all,'' Odone says. ''All he needs is a little bit of myelin around the nerves. Who knows? He might recoup some functions. If he could start talking, it would change our life completely.''