Guns seized by Fairfax County police routinely have been traded to private gun dealers in exchange for needed police weapons, a measure that is now being criticized by county leaders because of the risk that guns could end up back on the streets in the hands of criminals.

In the last four years, 655 semiautomatic handguns, revolvers, rifles and shotguns have been traded to licensed dealers, according to department records. The practice, which began as a cost-saving measure during the county's budget crisis of the early 1990s, is unique in the Washington area and stands in stark contrast to recommendations by national law enforcement groups.

All of the other major jurisdictions in the region, including the state police in Maryland and Virginia, melt down seized weapons after they are no longer needed as evidence. The International Association of Chiefs of Police last year urged all police agencies to destroy guns that are turned in or seized during arrests.

Fairfax police officials said no guns have been traded to dealers this year. But Board of Supervisors Chairman Katherine K. Hanley (D) said yesterday that she wants assurances that the practice has been stopped for good and will urge her colleagues to ban it at the board's next meeting on Monday.

"The Board of Supervisors needs to make it clear that under no circumstances will Fairfax County allow weapons seized, confiscated or turned in by citizens to be turned over to gun dealers for resale on the street," Hanley said.

J. Thomas Manger, who took over as the county's police chief in January, said yesterday that he supports ending the practice, but he did not criticize his predecessors for trading guns in tough economic times.

"We do it as a cost-saving measure, saving the taxpayers money. A lot of police departments do it. It's legal," Manger said.

Still, several supervisors said yesterday they were stunned to learn of the practice and will support Hanley's move to legislate an end to it.

"Dear God. I did not know. Frankly, I'm appalled to learn of it," said Supervisor Gerald E. Connolly (D-Providence). "They can get back into the streets. They can get back into the hands of the very folks we are trying to disarm."

Concern about the disposition of weapons by police agencies has increased nationwide since the discovery that the pistol allegedly used by Buford Furrow to shoot children at a Los Angeles day-care center in August originally had been used by a small police department in the state of Washington.

The Fairfax police department and those in most other Washington area jurisdictions have sent used police weapons back to the manufacturer or a dealer when they upgrade the guns issued to officers. That often gets the departments a break on the price of the newer models. When Arlington County upgraded its officers from 9mm Glock pistols to .40-caliber Glocks, the manufacturer offered an even swap, according to Cpl. Justin McNaull, an Arlington police spokesman.

But gun-control advocates and some top police officials say they also oppose the trade-ins of used police weapons because manufacturers often turn around and sell those guns on the market. Police agencies say they don't track the destination of the weapons after they have been returned to their makers.

When it comes to seized weapons, most jurisdictions have policies similar to those of Montgomery County, which two or three times a year sends a load of firearms to Bethlehem Steel in Baltimore, where they are melted down and the metal recycled.

In Virginia, the law gives wide discretion to judges, who can order confiscated firearms destroyed, given back to defendants or remanded to the police department.

At the court's direction, Fairfax police have destroyed hundreds of weapons. But other weapons are seen as a source of revenue. About 120 guns were traded to dealers in June 1997. An additional 317 long guns and handguns were traded to dealers in February and December of 1998.

In a recent memo, Fairfax police officials said there were no budgetary reasons to trade guns this year but left open the possibility that it could occur in the future. Manger said he was aware of the practice before he was promoted to chief. When he took office, Manger said, he decided not to engage in any gun trades because the department was flush with money and because such trades might be seen as questionable by the public.

"I've got no problem in the world" with halting the trades, he said. "It does not harm the police department in what we do one tiny bit. It's not something citizens want from their police department. Folks just don't think it's worth it."

Neither do more and more police officials.

Thomas C. Frazier, the Baltimore police commissioner, said he does not want the approximately 3,500 weapons seized by Baltimore officers each year to be used again.

"I think returning a handgun to the street is bad public policy," Frazier said. "Any way you slice it, that could be a homicide weapon and could cause the death of someone in the city or a police officer. I couldn't look a cop's widow in the eye."

The police chiefs association passed a resolution last October urging member agencies to destroy all seized firearms. "It did not make sense for us to be reintroducing guns back into communities we were sworn to protect," said Larry Todd, the chief of police in Los Gatos, Calif., who helped draft the resolution.

"It's our belief that public safety and the cost to society outweighs any economic value these weapons have when we're done using them," he said.

Database editor Sarah Cohen and staff writers Raja Mishra and Katherine Shaver contributed to this report.