A pair of American scientists who as co-workers and later as competitors worked out the basic biology of the sense of smell -- one of the body's most enigmatic and emotion-laden functions -- yesterday won the Nobel Prize in Physiology or Medicine.

Richard Axel of Columbia University in New York and Linda Buck of the Fred Hutchinson Cancer Research Center in Seattle shared the $1.36 million prize for unveiling the mysterious mechanism by which animals differentiate among the world's countless odors, which add so much to life's richness while providing potentially life-saving information about what's going on outside the body.

Odor is a big part of what is perceived as taste; to people lacking a sense of smell, most foods -- even some putrid ones -- taste alike. Odors are also notable for their ability to stir memories and emotions -- a function of the nasal lining's direct connection to deep and "primitive" parts of the brain. And as the world's perfumers have long averred, smell is an important mediator of personal attraction and perhaps even love.

In painstaking experiments conducted on odor-detecting cells lining the noses of mice, and in later experiments on human nasal cells, Axel and Buck found that as much as 5 percent of the genes in mammals were devoted to the sense of smell -- an astonishingly high percentage that reflects their importance.

Subsequent work showed that more than half of the 900 or so human genes devoted to detecting odors have mutated to the point of uselessness during the course of human evolution, evidence that people have gradually come to rely more on vision and hearing.

Still, the work has a range of practical applications, from the development of better tasting medicines to finding ways to block mosquitoes' ability to smell humans, stymieing their ability to spread malaria and other diseases. Some of the odor-detecting molecules identified by Axel have been patented by Columbia with an eye toward commercial application.

"This is an incredibly exciting area of neuroscience that was completely broken open by their 1991 paper," said James F. Battey, director of the National Institute on Deafness and Other Communication Disorders, the branch of the National Institutes of Health that focuses on the senses.

Before Axel and Buck's work, scientists had no idea how many genes might be involved in smell, how those genes behaved inside cells, or how the brain coordinated the information relayed by nasal cells to create a coherent perception of smell.

Eyes detect the full range of hues with just three kinds of receptor cells that detect one color each, leaving it to the brain to weigh those inputs and construct a composite tone. By contrast, the immune system detects and counters the spectrum of germs and other foreign bodies with a huge and diverse army, devoting one kind of antibody to each potential invader.

The nose, Axel and Buck found, hews closer to the immune system, with each odor-detecting neuron in the nose bearing just a single odor receptor, each able to detect just a few closely related odors.

They went on to show that all cells sporting the same detectors pool their signals at intermediate processing centers in the brain's olfactory bulb. The brain's cortex interprets that pattern of incoming messages as a particular smell.

In an interview yesterday, Axel, 58, said he got interested in the topic because he was looking for an aspect of sensory perception that might surrender its secrets to the tools of his specialty, molecular biology. Smell seemed like a good candidate, he said, because gene-finding techniques had grown efficient enough to identify the large number of genes that he expected it might take to detect the full palette of odors.

Still, he and Buck -- then a research fellow in his lab -- were "quite surprised," he said, to find about 1,500 such genes in the mouse, each responsible for making its own specific odor receptor, with only one such gene operating in any given nasal cell.

Axel, who was in California yesterday, said he learned of the award about 3:15 a.m. Pacific time, when he was awakened by a call from Swedish public radio. Ever the scientist, he did not comment until checking the evidence that he had won, by logging on to the Nobel committee Web site.

After that, he said, he made himself a cup of coffee, deciding to remain awake "to appreciate the moment."

In a telephone news conference from Seattle, Buck, 57, said the novel experiments, which took about three years, "didn't really have to work. There was a bit of luck."

Asked to describe the upbringing that helped launch her to becoming the 11th woman to win a Nobel Prize in science, she said her father, an electronics engineer, "did a lot of tinkering" and encouraged his three daughters to do the same. Her mother, a homemaker, was "obsessed with puzzles" -- another factor, Buck said, that may have inspired her.

Richard Axel and Linda Buck were honored for research that demonstrated the way in which animals differentiate odors.