The eyes get teary and the stomach weak. The gag reflex chokes the throat. Is that raw sewage? A rotting squirrel? The brain is too distracted to answer.

Pamela Dalton has uncorked the foulest smell on earth.

It comes from one of the vials that Dalton keeps under a ventilated hood in her laboratory, where the bottles carry impish labels: Burned Hair. Bathroom Malodor. And worst of all, Stench Soup, an odor so reeking of ripe Porta Potties -- or is it dead possum? -- that it fills the mind with white noise.

"That one takes over every aspect of your consciousness," Dalton says proudly of her creation, made in search of the world's most offensive odor.

Dalton is an expert in how the body perceives smells, a field shedding light on the workings of the nervous system, memory and emotion. But in recent years, her specialty has drawn interest from a less academic source: the Department of Defense.

Foul odors, it turns out, may be one of the most sensible ways for military commanders to disperse hostile crowds, empty buildings and keep intruders away from "no-go" areas. They are one of the most promising in the new crop of nonlethal weapons, intended to incapacitate people or equipment while minimizing the risk of death.

Nonlethal weapons are only a small part of the Pentagon's research and development program, but they received a major endorsement last week as a panel of the National Research Council called for a big boost in experimentation and spending. At the top of the panel's to-do list was increased study of foul smells, or "malodorants."

At the same time, some researchers are calling for renewed investment in nonlethal measures as a result of last month's hostage standoff in Russia. Authorities there used an opiate gas, intended to be nonlethal, to subdue armed Chechen guerrillas who had taken over a Moscow theater. More than 630 hostages were saved, but the gas killed at least 119 people.

"The Russians ended up having a lot of deaths because they didn't have adequate technology to act in a nonlethal way," said Larry Erickson of Kansas State University, which has researched the environmental effect of malodorants for the Navy. "It's appropriate for some of these studies to go on to find nonlethal ways to manage a variety of situations."

But nonlethal weapons could be counterproductive, some critics say. While seemingly humane, they might prompt an enemy to escalate the level of violence.

"It's laudable for the military to explore less lethal means of applying force, but they have to stay out of the chemical and biological area -- including malodorants," said Edward Hammond of the Sunshine Project, which opposes chemical weapons.

If the United States pursues odor weapons or even nonlethal chemicals, other nations would follow suit. Those nonlethal programs, Hammond said, could easily mask efforts to develop far more deadly chemical weapons.

The interest in "more humane" weapons dates to at least the 1960s. But military planners began to take them more seriously in recent years, as troops increasingly faced hostile civilians on peacekeeping or humanitarian missions in places such as Haiti, Somalia and Bosnia-Herzegovina. With TV cameras ready to broadcast civilian deaths worldwide, soldiers often had to navigate rock-throwing crowds with only two choices: the bullhorn or the bullet.

A critical boost came in 1995, when Marine Lt. Gen. Anthony Zinni asked for an infusion of nonlethal weapons, such as rubber bullets, to help him manage the final withdrawal of United Nations forces from Somalia. The next year, the Pentagon created an office to focus on nonlethal weapons.

Now researchers are developing slippery sprays that cause vehicles to lose traction. Underwater rope barriers could soon protect U.S. vessels, an attempt to head off disasters like the attack two years ago on the U.S. destroyer Cole in Yemen by a small boat laden with explosives.

Lasers and other energy beams are being studied for their ability to cast a confusing glare, immobilize vehicles or disperse crowds with a harmless but burning sensation in the skin.

These efforts are tiny by Pentagon standards, with between $20 million and $34 million spent each year, but now the Pentagon is being urged to do more.

Rubber bullets and similar devices are in the field, but these target individuals or small groups. "Demand is growing for more capable systems with wider-ranging effects," said the National Research Council panel, which advises the government on scientific matters.

It singled out odor weapons as among the most promising nonlethals.