Along M Street in Georgetown yesterday, there were harbingers of mayhem's descent. Shoppers bustled, arms filled with balloons and booze with which to boost the coming Bacchanalia. Here and there, a bizarre mask was donned.

Inside shops and restaurants, strategy sessions were under way.

Merchants were bracing for the ghostly visitors and pagan partiers that will flood their street of commerce today during Georgetown's annual Halloween hoopla.

With only a smidgen of resentment, most businesss people were willing to welcome D.C.'s one-day version of Mardi Gras.

"I love it. I mean, I'm an urban animal," said Dan Fendrick, owner of the Fendrick Gallery, who, outfitted as an Arab sheik, will attend a loft party -- in New York's Soho section.

More Scrooge-like, Scotty Feldman, an owner of Potomac Wine and Spirits, said he didn't want to hassle with "foreign spirits."

"I don't put up with any foolishness. I just don't tolerate it. They can come in and say 'trick or treat,' but that's it."

All over the District, kids and adults, police and civilians, were gearing up for big and hopefully safe fun. On a lesser scale than Georgetown's annual bash, there will be Halloween events in recreation centers all over the District.

"Any kid, any neighborhood, any age -- even the senior citizens -- will have a party," said Linda Wharton Boyd of the Department of Recreation.

Plenty of trick-or-treaters are expected to be out despite a trend toward more organized and confined events that began for safety's sake, Boyd said, about four years ago. A nationwide increase in the number of incidents where children fell prey to pranksters -- mainly candy and apple tampering -- has led many parents to call for more supervision.

District police say they have no record of any candy tampering on Halloween last year. Greater Southeast Community Hospital, which has for three years used X-rays to screen candy for foreign objects such as pins or razors, has yet to find anything, said Ann Cahill, a hospital spokeswoman. The hospital will continue the screening this Halloween.

Boyd suggested that parents go trick-or-treating with their children and inspect any candy they collect, especially if it is unwrapped. No child should venture out alone, especially after dark, Boyd and others said, pointing out that there is safety in numbers.

That theory does not necessarily hold true when talking about the huge number of Halloween revelers expected in Georgetown tonight. Police estimated the size of last year's crowd at 100,000, and are expecting a similar number this year.

Although police officials will not say exactly how many officers will be deployed in the target area between 29th and 34th streets and K and R streets, last year a contingent of 500 officers was on hand. And, like last year, some police officers will be in uniform and some won't.

"They just won't know who we are," police spokesman Quintin Peterson said. "We might have on costumes, we might not."

Last year in Georgetown, police made 35 arrests for infractions such as carrying open containers of alcoholic beverages and public urination, he said.

That crowds can get unruly goes without saying, according to Al Aidara and Reza Golbadi, managers of Dash's Designer, a men's clothing store.

"People are drunk, taking the shirts off the shelves, screaming," Reza Golbadi said. "You cannot tell them anything because they are in a high mood."

When asked what Crown Books would be doing on party night, manager Mark Reagins laughed: "Protecting the store with a baseball bat." He said people wearing costumes won't be allowed in the store. "Any smart, intelligent retailer would do that."