The vacuum cleaner business must be booming in Essex, because Big Mike McCarthy is getting the same answer at almost every house.

"Just bought a new one last week," a smiling woman says through a screen door.

Big Mike fended off the rejection politely and gave it one more shot, handing the woman a tiny plastic bag of wood chips.

"If you just walk around and agree with everyone, you'll never get in," he said over his shoulder.

"This is a free gift from me," he said in a fast mumble. "Just scatter them on the rug and vacuum them up. Makes the room smell nice. Let me show you."

She laughed, took the chips and closed the door. Big Mike's first trick of the day didn't work, but he had more "sales enhancers" in the pockets of his light blue slacks.

He shrugged and hiked his 6-foot-4-inch, 220-pound body, varicose veins, and 16-pound Electrolux 3500 deluxe vacuum cleaner up the street, muttering, "She might even be telling the truth."

Michael Timothy McCarthy, whose grandparents were from County Cork in Ireland, is part of a tough and dwindling breed of men and women who sell door to door, accepting constant assaults on their self-esteem as part of the job.

Door-to-door salesmen have long been a staple of American society. Alfred Fuller, perhaps the most famous of them all, began selling brushes, brooms and mops that way in 1906.

"He may not have been the first, but he was the first to make it work in a big way," said spokeswoman Becky Weller from Fuller Brush headquarters in Great Bend, Kan.

The Fuller Brush man is no longer a familiar figure at the door. Telemarketing, home parties and other methods have slowly replaced the old routine.

After 25 years in the business, Big Mike, now 50, knows how to fight rejection.

On this hot afternoon, he psyched himself up as he walked a quiet urban street.

"I know there's a sale here," he said, peering around intently. "I can feel it."

He had cased the neighborhood just off Mace Avenue in his rusty 1986 Ford van -- which showed all of its 325,000 miles -- before settling on a street with a lot of cars parked along the curb. "People are home," he said, and indeed they were, mostly working class, retired people living in modest brick and aluminum-iding-covered homes.

He approached a woman holding a squirming child by the hand as she left her mother's house. Big Mike stepped forward with a friendly wave and his best Irish smile.

"She's got her hands full, but you never know," he said.

The woman lived nearby and agreed to let him shampoo her rug that night.

"You can't prejudge," he said. "I sold a vacuum to an elderly woman one day who pulled $800 in cash out of her mattress.

"Rejection beats some salesmen down, but you just laugh and move on."

When Big Mike isn't out selling, he lives with his wife and two children in a quiet, single-family development in Cockeysville.

He's a Baltimore native, the son of a John Hancock insurance salesman. He spent nine years starting in his late teens as a brother with the Oblates of St. Francis DeSales in Philadelphia before he started with Electrolux.

"My mother -- who's 86 -- told me I should learn to sell because you can always go out and do it anywhere, any time, and you're never out of a job," he said.

None of this was on his mind as he headed toward the next house. Big Mike works a street the way a farmer plows a field; straight on, unwavering, convinced that hard work will yield some shimmering green.

"I can't fool around," he said. "A cruise to Mexico is on the line."

April and October are the spring and fall cleaning months, when vacuum cleaner companies step up their promotions and offer bonus incentives to their salesmen.

Big Mike needed 50 sales. He had 37 with only five days to go, a nasty challenge even for someone with his experience.

"You tend to focus on the trips, and forget how much money you're making," he said.

The money can be considerable. Good salesmen are happy to show you their pay stubs to prove it.

Big Mike's best year was in 1982, when he grossed $81,000. Last year he made about $60,000, but admits he has slowed down now that he's older and has money put aside for his two children's education. His oldest child, Jennifer, will graduate from Indiana University of Pennsylvania this month.

"We worked the streets together during her summer vacations," he said.

The top seller last year at the Electrolux branch on Rossville Boulevard where Big Mike works out of was Al Lewis, who grossed $79,000. Many of Mr. Lewis' sales came through telemarketing, but he still does some door-to-door. As do the other expenses, telemarketing costs come out of the salesman's pocket, which is one reason why Big Mike doesn't do it.

"Telemarketing is for the '90s," Al Lewis says, "and I don't go home with tired feet."

Big Mike had tired feet and wasn't earning a nickel on this cloudless, 92-degree day. A man working in his yard didn't want to be bothered, but took Big Mike's card.

Big Mike went to the next house, knocked and stepped back.

"Don't crowd the customers," he said. "You might scare them. Be casual, but not too casual. Make the customer feel comfortable. It doesn't matter what you say, because they're not listening anyway.

"They're watching what you're up to."

What has changed the most in his 25 years on the street?

"That's easy," Big Mike said. "The two-earner family."

That's good news and bad news for door-to-door salesmen.

"It's harder to catch people at home during the day now, but then, they have more money to spend," said Jay McDonald, the Electrolux branch manager. This trend has led to an emphasis on the "golden hours," from 6 p.m. to 9 p.m., when the man and woman are usually at home. "We tell the salesmen, 'It's a beautiful day to work, and you can stay out there till 9 or 10," Mr. McDonald said.

That was Big Mike's intent, and he pushed on after 20 fruitless calls.

"There's no salesman in the world who doesn't get discouraged," he said.

"You just have to have the right attitude. It takes a lot of self-discipline. You have no excuses. There's just you, the street, and a bunch of houses.

He knocked on a door. An elderly woman answered, but she wasn't interested in cleaners. She just wanted to complain about how much money she had put into Social Security.

Big Mike smiled and moved on. "You have to know when you're wasting your time," he said.

It was time for another "sales enhancer."

The next woman had two new vacuum cleaners, she said, and Big Mike gave her a gift certificate for a rug shampoo. She looked at it dubiously and stuck it in her pocket.

"It's a $39.95 value," Big Mike said. "Nice to see a friendly face."

He started to pass a house that needed painting. "No money there," he said, then stopped short.

"Uh oh, new windows, and a new air conditioning unit on the side of the house," he said. He knocked on the door. There was no answer but he wrote down the address. Big Mike never misses a clue.

An elderly woman with a cane passed by, saw his Electrolux, and called out loudly the name of a competing vacuum cleaner: "Rainbow is the best!"

"You're right, madam," he said, then turned his head, the smile gone. "She's just looking for someone to agitate, and she found him."

A woman in her 60's answered the next knock. She said she had an Electrolux and was about to use it.

Big Mike glanced in the door and said, "Darned if she doesn't."

"I'm not selling today, so I'll check it out for you, see if it's OK, and fluff up your rug," he said.

The woman said she had another vacuum upstairs -- a competitor's -- that cost her $1,000.

"Good machine. You should have got a TV with it for $1,000," Big Mike said. "Has the handle broke yet?"

Big Mike checked her machine, then ran his. "See that little headlight, that's new," he said.

She said she was moving into a trailer soon. "Just the ticket for a trailer," he said quickly. She also said she had a friend in Dundalk who needed a vacuum.

"Don't want to be pushy," he replied, a gleam in his blue eyes. "Just give me her phone number."

He went for the knockout, pulling out the ultimate enhancer, a picture of a hand-held dusting vacuum.

FTC "Sells for $60, but I'll give it to you if I sell your friend," he said. The cost would come out of his pocket.

"Hmmm, I'll surely call her," she said, taking Big Mike's card.

L "People usually say 'OK' for something free," he said later.

He walked down the street, his energy flagging in the hot sun after almost three hours and 35 houses.

"Not many people want to do this," he said. "There's no prestige in door-to-door selling. People are too proud to do it."

Does it bother him?

"No, but I'm one of the few it doesn't," he said. "It's why I've lasted so long. But my children were happy when I became a branch manager and they could tell people that."

Big Mike was a branch manager for 10 years, but went back on the street because he got tired of trying to recruit new salesmen, the industry's biggest problem.

"People who've been laid off could come out and make good money, but they don't want to tell their friends they're going door to door," he said.

The branch manager brings in 15 to 20 people a month for a tryout, but few stay with it.

"They can't take the rejection and competition, but the biggest competition," Big Mike said, tapping his head, "is right here."

He broke for a cold soda, then headed for North Point on a service call. He made a double sale, a vacuum and a shampooer to a retired couple.

The next day he went to Kent Island, where he rolled up three sales.

"More people are at home in the country," he said.

He drew a blank in Gardenville on Wednesday, but scored the next day with three sales to a cleaning service and a shampooer to a home customer in Gardenville.

He still needed four sales in three days to make the cruise to Cozumel. After striking out on Thursday, he sold a shampooer and vacuum in Gardenville on Friday, and two shampooers in Parkville the next day. That made 50 units and a cruise.

L "They're out there," he said. "You just have to work at it."

9- That he would make it was never in doubt.