Last night's humongous street party in Georgetown had all the earmarks -- if that's the right word for the steak knife in Andrew Matosich's right temple -- of a back-to-basics Halloween.

"It's really very simple," explained the blood-spattered George Washington University student, standing in the crush at Wisconsin Avenue and M Street. "I just held the knife out here in front of my face, and concentrated for a long, long time."

Matosich, whose getup was hideously persuasive, was on the cutting edge of what looked to be a traditional Halloween celebration of the gory, the ghostly and the ghastly.

"I think that in the past," said federal employe James Reeves, "too much of the spirit of wonder, terror and confusion had gone out of Halloween. There were just too many cute ghosties and Hallmark cards." Reeves, who'd come as a giant fur-covered tarantula on wheels, was clearly in the ghastly category.

Shortly before 9 p.m., the police relented to wonder, terror and confusion and closed Georgetown's M Street jugular, as well as Key Bridge, to cars. Witches, warlocks, vampires and goblins led the first wave that broke into the intersection. They were followed by a platoon of killer bees, a family of coneheads, a herd of elephants and an ambulatory commode.

Police said about 25,000 people were on hand shortly before midnight, and one city officer estimated that 40,000 would pass through the area before it was all over. According to police inspector R.J. Pennington, that made this Halloween Washington's biggest -- "by a little bit" -- since the tradition was started in the mid-1970s by club owners trying to put some zing into Georgetown's night life.

It was hard to see how Georgetown ever lacked it. As the traffic streaming into the area from Foggy Bottom reached gridlock, some drivers got out of their cars and danced on their hoods. Others shared their critical appraisals with revelers on the sidewalk. "You look like the Rainbow Coalition," one of them shouted at a fellow with multicolored hair.

Police had made a dozen minor arrests by midnight and Pennington called the crowds "orderly and congenial."

The weather was clear and appropriately balmy.

"This is a great night for people to return to their youth and live out their fantasies," said restaurateur Michael O'Harro, who claims to have tossed one of Georgetown's first Halloween bashes, at the now defunct nightclub Tramps, in 1975. "It allows the Casper Milquetoast junior executive to be the evil ruler or the Viking king. And it lets the secretary from the motor pool be a lady of the evening or the punk rock queen."

Last night's party -- Washington's answer to Mardi Gras -- was a spontaneous event waiting to happen.

"There are not too many places in Washington where you can be spontaneous," said Joe Corey, whose costume consisted of black and white stripes on his face and a beer can in the breast pocket of his tuxedo, "and Georgetown seems to lend itself to spontaneity in that regard."

As he spoke, a conga line began to swirl in the middle of the intersection, followed by a chain gang in striped pajamas. Around portable tape decks formed pockets of breakdancers while Playboy bunnies and pregnant nuns joined in rhythmic shouts and primal screams. From Cafe Broadway, a cocktail hostess dressed as Cleopatra could gawk through the plate glass windows at Cleopatras dressed as cocktail hostesses.

"I think it's absolutely superb -- America at its best," said John Fenely, a bow-tied academic from Oxford, England, who was making his first foray into a Georgetown Halloween. "I'm a medievalist, so you see I'm well-versed in Halloween, although we don't do it in England. I think the primitive Scots had something like it where they hid behind doors and scared people."

"My whole life is Georgetown," said Mary Fortuna, a 16-year-old high school student from Bethesda, dressed as a French clown. "I love it. It's my favorite place in the world. I want to come here until I die."