along with little Mr. T's, Masters of the Universe and a smattering of clowns -- are expected to invade the area today, and local groups have conjured up haunted houses, costume parties and treat-or-trick brigades to keep the child's play from turning into horror stories.

"It's a big night for the children and we just want it to be a safe one," said Gloria Vessels, spokeswoman for the D.C. police, who added that there are no tricks that can replace simple precautions.

"We are just trying to warn the parents and the children to be on the lookout for anything out of the ordinary," she said.

Several local hospitals have announced hours during which they will X-ray bags of treats to make certain no harmful objects have been hidden in them.

But Vessels and others warned that supervision should also be provided for the revelers, along with a flashlight or reflective markings on their costumes.

Recreation agencies throughout the area will sponsor afternoon and early evening parties that should permit young children to finish their rounds by a little after dark -- and get off the streets by the time older ghouls are ready to play.

Carolyn Mills, a city Recreation Department spokeswoman, said 108 recreational centers in the District have scheduled Halloween festivities as an alternative to traditional trick or treating.

But even those free festivities -- games, dancing, costume competitions and apple bobbing -- will be held under tighter security than in previous years, Mills said.

Recreation workers are making sure the centers and adjoining playgrounds are well-lighted and the hedges trimmed so as not to provide a cover where someone could lurk.

Strangers are not welcome and loitering will be discouraged, Mills said. Most of the activities will begin shortly after school for elementary-school-age children and end as late as 10 p.m. for high-school-age youths, Mills said.

About 180 police officers will patrol the Georgetown area -- in recent years a focal point of Halloween celebrations here -- and will set up sobriety checkpoints, police said.

There is no plan to close Georgetown streets, but there will be parking restrictions: from 4 p.m. parking is prohibited on M Street between 28th Street and Key Bridge, and on Wisconsin Avenue between K Street and P Street. "Tow trucks will be on hand to immediately remove them [cars]," said Lt. John Bowden of the D.C. police. "We'll be very strict. We'll have teams of officers to move anywhere in Georgetown within a matter of minutes. We'll be there to remove them -- those who start fights -- very quickly."

Other communities are planning for a more sedate Halloween, although many cities and counties plan to have additional police on duty.

Prince George's County police, among others, are urging families to restrict their trick or treating to between 6 p.m. and 9 p.m., to discourage vandalism.

The towns of Cottage City and Riverdale have banned trick or treating completely, but areas will sponsor Halloween parties for children who live there.

There is a 10 p.m. curfew in Leesburg, Va. "Any person violating this ordinance could be charged no less than $1 and no more than $10," Police Chief James Kidwell said.

The town of Cheverly is permitting trick or treating only for children through the sixth grade, with residents asked to keep a porch light on if offering treats.

In Greenbelt, trick or treating is from 6 p.m. to 8 p.m., with homeowners asked to keep porch lights on, and apartment and condominium owners asked to tie a white cloth on the doorknob if they are offering treats.

In Prince William County, about 350 residents from the area's Neighborhood Watch programs will help police patrol the county's 75 to 80 communities, according to police there.

Listed below are some Halloween tips:

* Parents or older, responsible siblings should accompany children for trick or treat.

* Children should have a working flashlight and wear a light-colored costume or clothing, which should be of nonflammable or flame-retardant fabric and short enough that younger children won't trip on the hems.

* Trick or treat celebrators should go only to homes with outside lights as a sign of welcome. Those receiving children should remove any possible obstacles from steps, lawns and porches.

* Parents should check all candy and fruit before letting their children eat it.

Area hospitals offering free X-rays of Halloween treats tonight and tomorrow:

DISTRICT OF COLUMBIA

Washington Hospital Center, 4 p.m. to midnight, Wednesday.

Providence Hospital, 4:30 to 11 p.m., Wednesday and Thursday.

D.C. General Hospital, 4:30 to 9 p.m., Thursday.

VIRGINIA

Alexandria Hospital, 8 a.m. to 4:30 p.m., Wednesday and Thursday.

Fairfax Hospital, 6 p.m. to 10 p.m., Wednesday.

Jefferson Memorial Hospital, 4 p.m. to midnight, Wednesday.

Arlington Hospital, 1 to 4 p.m., Thursday.

MARYLAND

Montgomery General Hospital, 9 a.m. to 9 p.m., Wednesday and Thursday.

Prince George's General Hospital, 6 p.m. to midnight, Wednesday.

Doctor's Hospital of Prince George's County, 7 p.m. to 9:30 p.m., Wednesday.