For Clinton resident George Leftwood, it was a matter of convenience: He saw a self-employed home contractor working in the neighborhood and asked him to make some improvements to his own yard and house on Keebler Drive.

Two years later, however, Leftwood's yard is unimproved and his porch is still in disrepair. And the $4,000 he gave the contractor is gone. "All he did was lay three cement slabs," Leftwood recalled wearily last week. "He never did come back."

Leftwood appealed to the Prince George's County Consumer Protection Commission, and a hearing panel directed the contractor to make a partial refund, but no money has been recovered. The director of the commission says this and one other judgment against the contractor have been sent to the county attorney for enforcement in court.

Local consumer agencies say George Leftwood's experience is repeated in scores of neighborhoods throughout the Washington area each spring, the season when homeowners most often fall prey to unethical, unlicensed home improvement contractors.

"Spring is when they all come out," said Eric Friedman, consumer specialist with the Montgomery County Office of Consumer Affairs. "That's the time of year people think in terms of spring cleaning, home repair."

To perform home improvement work in Maryland, contractors must be licensed by the state. Working without a license is a misdemeanor.

Consumer and legal experts say that this time of year, contractors scour neighborhoods soliciting work door-to-door, the unethical ones insisting that they will guarantee work at bargain rates. But they rarely perform the work as promised, the experts said.

"He's doing his business out of his hat; he doesn't have a fixed location, a fixed address, and you can't put your hands on him," said Matthew Green of the District's Department of Consumer and Regulatory Affairs, describing the typical unlicensed contractor. "That's the real problem."

It is a problem across the country; nationally, the Better Business Bureau received more than 32,000 written complaints last year about home improvement contractors.

Locally, the Better Business Bureau of Greater Washington received more than 750 complaints last year from residents of the District, Maryland and Virginia. The complaints trickled in during the early months of the year and doubled in late summer, a spokesman said.

The Prince George's commission reviewed 150 complaints about home improvement work last year, its largest single category, a spokeswoman said. Most complaints are resolved either by having repairs completed or money refunded, commission official Eileen Brandenberg said.

The commission can impose fines, but only for multiple offenses. Where unlicensed contractors are involved or work has been abandoned, the commission recommends that homeowners take their complaints to the Maryland Home Improvement Commission, which can take criminal action, Brandenberg said.

Vince Demarco, the assistant Maryland attorney general who is council to the commission, said that of 2,829 complaints brought to the state commission in the year that ended last June, 2,607 of them were resolved. Most are settled informally by an investigative unit of the commission, he said.

"A lot of times there is miscommunication" between homeowners and contractors, he said, "and someone from here talking to both parties can resolve it." Thirty contractors' licenses were suspended during the year and two were revoked, he said. Unlicensed contractors can be fined up to $2,000 by the commission.

Montgomery County consumer affairs specialists handled 703 home improvement complaints last year, 59 percent of which were resolved to the homeowners' satisfaction, consumer affairs director Barbara B. Gregg said.

The District's Green said the problem of unethical contractors exists "wherever there are homes in a state of disrepair" that are owner-occupied.

In addition, home improvement contractors often look for work in newly built subdivisions where homeowners are interested in finishing touches such as landscaping, said Donna S. Crocker, director of the Prince George's commission.

In financial terms, the problem is perhaps more serious than mail order and auto repairs, also among the top consumer complaints, consumer protection officials said. "If you were ranking by how much money was spent, it would be No. 1," Crocker said.

Consumer advisers say such problems with itinerant contractors can be avoided.

City and state governments require small contractors to be licensed, meaning that they must have proper insurance and post surety bonds. They should be able to show their licenses to prospective customers, officials said.

But most itinerant contractors are unlicensed, the officials said. In the worst cases, they give their customers business cards with ficticious phone numbers and addresses. "Consumers don't do enough checking before they give someone $7,000, $8,000 or $9,000," Green said.

High-pressure sales pitches often lead to the impulse contracting, advisers said. "The man offered a super price for what he was going to do," Oakton resident Robin Carter said of her experience with a contractor two years ago. The man had used a pitch familiar to consumer protection officials: He said he needed to use the paving materials left over from a job nearby and offered to pave her driveway for a third of the normal cost of $1,200.

"The guy did a lousy job, even for $400," Carter said. "Actually, it looks worse than it did before."

District consumer and building authorities say they have many complaints about shoddy roof repairs by itinerant workers.

In Maryland, officials this spring have begun cautioning residents about unlicensed furnace cleaners who have been soliciting work door-to-door in the area under the business name "Maryland Furnace."

"A group of individuals claim they can offer reduced group rates because they are working in the area or say they were referred by a satisfied neighbor," the Prince George's consumer agency said in an announcement. That should be a red flag that they are not licensed to do such work within the county, officials said.