Most of the bats considered problems -- like when they are in your living room -- are young ones, says "bat advocate" Phoebe Wray, and the most common time for problems is late summer, when they are first trying their wings and are bound to have a few mishaps.

* To tell if you have bats living with you:

"Check around the eaves of your house for tarry little smudges." Bats can get in not only chimneys and air vents, but cracks as small as three-quarters of an inch. Those smudges, by the way, are not dirt, but oil from the bats' wings.

* If you have a bat in your house:

"First, confine it in one room and open the windows," advises Guy Hodge of The Humane Society of the United States. "It should fly right out."

If that doesn't work, you can wait until daylight when the bat is tired, and likely to be hiding behind your drapes or some other dark place. Capture it in a coffee can or some other container and take it outside and release it. Wearing gloves, says Hodge, isn't a bad idea.

He says people also have reported capturing bats in butterfly nets, but notes that you have to catch it from behind: Its sensitive echo-location system will help it avoid anything coming at it from the front. Forget the broom. "You won't accomplish a thing."

You should never approach a bat -- or any wild animal -- that's on the ground or appears sick or injured. If you find a downed bat, or if you're scratched or bitten by one, call Vector Control in the District, 576-7389. (Because of the possible threat of rabies, be sure to keep the bat.) In the suburbs, call the animal-control agency under your local government listing.