URICH — In a quiet village on the outskirts of Zurich, a genetically engineered strain of rice that its creator says could save millions of children's lives is locked up in a grenade-proof greenhouse as if it were the Frankenstein monster that some critics contend it is. Unlike any other rice on earth, this so-called golden rice produces beta carotene in its seeds, thanks to genetic instructions that scientists added to the rice from a daffodil, pea, bacterium and virus.

Beta carotene is an important source of vitamin A, which is crucial for healthy vision and resistance to disease. The body breaks beta carotene molecules into two vitamin A molecules, also known as retinol. People get beta carotene from fresh vegetables, like carrots, and get vitamin A directly from milk, butter, cheese, liver and cod liver oil.

But the World Health Organization estimates that 124 million children do not get enough vitamin A. Most of these children live in parts of the world where rice is not only the main staple but is often the only food available during the dry season, and infants are often weaned on rice gruel alone. Vitamin A deficiency causes about half a million children to go blind every year and makes many more vulnerable to diseases that cause diarrhea. One million to two million children die each year for lack of vitamin A.

Like a latter-day Johnny Appleseed, Dr. Ingo Potrykus, the German inventor of golden rice, would like to send his seeds to poor people around the world at no charge. "I would like to send a year ago," he said, holding out a handful of seeds stored in a locked refrigerator at the Swiss Federal Institute of Technology in Zurich. "There are 3,500 children dying every day. I think we should not delay one day."

But golden rice has remained under lock and key since it was created more than a year ago. Meanwhile, Dr. Potrykus has struggled to free it from a complicated web of more than 70 patents and legal agreements covering items as diverse as DNA sequences and the techniques he and his colleagues used to insert new genes in the rice. He is also racing against an effort to pass legislation that could prohibit the export of genetically modified organisms from Switzerland.

Dr. Potrykus hopes to be able to send out the seeds before the end of this year under an agreement he worked out with Zeneca Agrichemicals, which has patents on some of the crucial genetic instructions used to make the rice.

The deal was brokered by Greenovation, a small German company that specializes in licensing academic discoveries in biotechnology. Greenovation licensed golden rice from Dr. Potrykus and Dr. Peter Beyer of the University of Freiburg in Germany, who collaborated on the invention.

Greenovation then licensed golden rice to Zeneca Agrichemicals, which last week merged with the agricultural divisions of Novartis to form a new company called Syngenta, now the largest agricultural biotechnology company in the world.

The company plans to market golden rice in developed countries like the United States as an enriched crop containing antioxidants, which are believed to reduce the risk of cancer, heart disease and macular degeneration, an eye disease that leads to blindness.

In return, Zeneca Agrichemicals agreed to secure rights to other patents covering golden rice and grant the inventors a license to give golden rice away to international research institutes that are working on developing new varieties of rice in places like India and the Philippines.

The genetically engineered rice will be crossed with local varieties using traditional breeding methods, and health and safety tests will be conducted.

If everything goes well, within two to three years, golden rice varieties will be made available free to farmers earning less than $10,000 a year from the crop, a figure far exceeding the average income of poor farmers.

Farmers will also be able to save seeds from their crop for future plantings because rice is a self-pollinating plant that breeds true year after year.

Dr. Potrykus held firm to those conditions through what he described as tough negotiations. But in some ways, the negotiations were made easier because the commercial potential for golden rice is expected to be limited, while the potential humanitarian benefits are great.

The inventors will earn a royalty on any profits from the niche market for health foods in places like the United States, said Dr. Adrian Dubock, who negotiated the deal on behalf of Zeneca. And the company agreed to provide Dr. Potrykus with a stipend and cover his expenses for the free distribution of the rice to researchers in developing countries. But nobody will get rich from golden rice, Dr. Dubock said.

The free distribution of golden rice seeds and genetic materials will be guided by a humanitarian advisory board consisting of the inventors, Dr. Dubock, representatives from the countries where golden rice will be grown, and Dr. Gary Tonniessen of the Rockefeller Foundation in New York, which supported the golden rice research.

Golden rice could serve as a model for arrangements to share proprietary biotechnology where it is needed most, predicted Dr. Tonniessen, who oversees grants to improve food supplies and nutrition worldwide.

The foundation is talking with international agricultural research centers, biotechnology companies and the World Bank about creating a nonprofit holding company that would make such discoveries freely available for humanitarian purposes.

"Golden rice is just one crop and one trait," Dr. Tonniessen said. "The potential to improve the nutritional content of many crops in many ways is now technically feasible."

Dr. Tonniessen said the idea for golden rice came from the field in developing nations. He once asked plant breeders at the International Rice Research Institute in the Philippines what they would choose if they could have genetic engineers insert any gene in rice.

The answer was a gene to make rice seeds produce the yellow pigment beta carotene, a trait they had not found in any rice variety and therefore could not propagate by traditional cross breeding. Although beta carotene has no taste, researchers are concerned that consumers in Asia might not like the yellow color because whiteness is highly valued in rice. Still, they hope people will feed it to their children.

The key to producing golden rice came from a scientific collaboration that began at a brainstorming session sponsored by the Rockefeller Foundation in New York, where Dr. Potrykus met Dr. Beyer, who had figured out how beta carotene was produced in daffodils by isolating the biochemical steps that make the flower yellow.

In 1993, the two scientists' laboratories began working together to put the three essential genes from a daffodil into rice. But one of the genes did not work. Over the years, they jury-rigged a combination of genetic instructions from a daffodil, pea, bacterium and a virus to make the beta carotene molecule. They still had trouble getting the genes to work together after shooting them one at a time into rice embryos. Finally, last year a researcher in Dr. Potrykus's lab, Dr. Xudong Ye, tried using a bacterium to ferry the instructions in all at once. It worked.

From the outside, golden rice plants look just like other rice plants. It is only when the seeds are hulled and polished to remove the oily outer coating, which is usually done to protect rice from spoiling, that one can see why Dr. Potrykus calls it golden rice. The seeds glow with the yellow color of beta carotene. Golden rice is a dream come true for Dr. Potrykus, and he is noticeably relaxed among the plants in his greenhouse. "It's a very beautiful plant," he said, stroking the graceful green leaves and cascading pearly seed heads.

Dr. Potrykus, 66, has spent his entire scientific career learning how to transform rice. His ultimate goal was to redeem genetic engineering by proving that it could contribute to solving malnutrition, which he sees as the biggest problem in the world. This calling has roots in his childhood, when he was an 11-year-old refugee from eastern Germany after World War II. His father, a doctor, died in the last days of the war. He and his brothers had to beg, steal and scrounge for food.

"I have experienced myself what it means to be hungry," Dr. Potrykus said. And as long as the potential of golden rice remains locked up here in Switzerland, he remains palpably angry and frustrated.

In the past decade, genetic engineering has become controversial, as some consumers raise concerns about the potential health and environmental effects of what they call "Frankenfoods." Dr. Vandana Shiva, a prominent opponent of genetic engineering in India, has argued that golden rice is being "used as a Trojan horse to push genetically engineered crops and foods."

Golden rice has become a high- profile target partly because it is being heavily promoted by the agricultural biotechnology industry as the first genetically modified crop to benefit consumers rather than just farmers and agribusiness.

And for better or worse, Dr. Potrykus has become a symbol. He headed the largest scientific research group at Switzerland's top technical university, where he directed 64 researchers investigating ways to improve nutrients and disease resistance in basic food crops. Although he enjoyed the formal respect that accrues to "Herr Professor," the highest honorific in the German speaking university, Dr. Potrykus found himself being put on the spot in increasingly unruly public debates. At one point, he said, he feared for his safety when hundreds of students shouted him down in a lecture.

Nothing has ever happened to Dr. Potrykus or the greenhouse that he built to isolate his experiments from the environment and any foreseeable attack. But by the time he and his colleagues finally succeeded in making rice produce beta carotene last year, after a decade of setbacks, Dr. Potrykus had reached the mandatory retirement age. And Dr. Potrykus said his wife wanted nothing more than for him to "stop being engaged and start a peaceful life."

They live in a small village more than an hour's drive from Zurich, but even there his wife feels unsafe. "If the genetic engineer is in the public opinion the devil," Dr. Potrykus said, "you cannot feel happy wherever you are."

Dr. Potrykus said he would like to retire and pursue their shared passion for chasing rare bird sightings around Europe for a videotape atlas he is compiling. As long as his mission remains unfulfilled, however, bird-watching must remain a hobby.

So Dr. Potrykus continues to work from an office in his home, responding to criticisms on the Internet and finalizing plans for distributing golden rice. And although his lab has been dismantled, he has re-enrolled at the institute as a postdoctoral student so he can continue tinkering with rice.

A colleague is sharing a desk with him. And he is working with the only two members of his team remaining at the institute to try to increase the amount of iron in rice in order to combat anemia, another scourge of people who subsist on a diet of rice and little else. Anemia affects about two billion people, especially weakening children and pregnant women.

Dr. Potrykus said golden rice had received considerable attention, but he considers boosting iron in rice to be even more important. "The potential for this technology is immense," he said, "but only if it's really used and applied to practical problems."