They were serious grown-ups -- lawyers, accountants, secretaries, college students -- engrossed in child's play.

They huddled around the sales counter and clothing racks, giggling and whispering about their secret plans.

The bewitching spirit of Halloween strikes Saturday, and yesterday, stylishly dressed professionals spent their lunch time trying to recapture the zaniness and devil-may-care attitude of their childhoods.

"I have a man over here who wants to look like Dracula," a sales clerk shouted in the crowded Ronna Costumers shop at 1139 18th St. NW.

Nearby, a woman eyed a Raggedy Ann outfit, while another customer was choosing accessories for a Statue of Liberty costume.

"It brings back my younger days," said Debbie Stewart, a secretary, who along with her sister Nina poked through the rows of costume racks. "Life is so uptight on your day-to-day job," Stewart said. "Halloween is good relief. That 9 to 5 can kill you."

For Stewart and other grown-ups, Halloween is serious fun. In recent years, more adults, particularly between the ages of 30 and 50, have joined children in celebrating the American tradition, local costume shop owners said.

"It used to be for kids," said Karen Katz, division manager of Masters Costumes in Baileys Crossroads. "Then there was the candy tampering scare a few years ago, which put a damper on trick-or-treaters. Now, it's an adult holiday too."

Although adults don't go door-to-door, they do wear their costumes to house gatherings and galas. Katz said sales have been brisk in the last few weeks, and she expects to be sold out of the store's 1,000 costumes as usual by tomorrow.

Costumes not only seem to change from year to year, but also differ in each region of the country, costumers said. This season, Jim and Tammy Faye Bakker of PTL fame; the California raisins from the popular TV commercial; Alf, the furry space alien with his own television show, and Spuds MacKenzie, the party animal spokesdog for Bud Light beer, are big here and everywhere, store owners said.

But because Washington is so political, many Halloween revelers will be dressed in the likenesses of President Reagan, the Ayotallah Ruhollah Khomeini and former House speaker Thomas P. (Tip) O'Neill Jr., three of the biggest sellers so far, costumers say.

But the traditionalists are there too, said Marsha Fratkin, an owner of Repeat Performance in Rockville. Women are interested in Cleopatra, while men want to dress up in martial arts suits and hooded robes.

For the truly younger set, girls under age 12 want to be princesses and ballerinas, Fratkin said. Boys just want "to be as scary as possible," she said.

Joyce Rucker, who recently moved to the area from New York, said she has celebrated Halloween every year for the past 10 years. "Nobody pays attention to you as long as you're civil," she said while trying on a white wig, glistening crown and red fire torch, replicas of Miss Liberty's attire. "I wanted something New York-ese."

But a group of young men summed up why they're big on Halloween.

"It's to pick up girls, I guess," said one man as he eyed a row of masks of Reagan, Dracula, Darth Vader and others. "You can hide behind the masks until you're sure you want to be identified."