ON A GIVEN SATURDAY, and this is one of them, local scavengers zero in on tourists' wallets. The visitors' cash and credit cards are safe, but deposit slips and receipts from banks west of the Mississippi River are a different matter entirely. They're worth 30 points to teams participating in the monthly "Great Limousine Races" staged by Amazing Adventures for Open University.

For $36 per person, teams of six or seven get a limo and driver for 3 1/2 hours as they scurry to five designated areas of the District seeking 85 objects (such as the western bank slips) and answers to sometimes obscure questions. The hunt, which begins and ends at the Old Post Office Pavilion, becomes a race because teams are penalized two points per minute for finishing after the deadline.

The winner of the most recent race, in March, was the Women's Adventure Club, whose "members" showed up in costume without ever knowing that they were going on a scavenger hunt. Organizer Sandra Ludwig of Arlington had told her friends only to show up wearing unconventional hats, colorful clothing and to bring a type of gourmet food.

"We yelled and screamed and drank champagne throughout the whole day," said Ludwig. "We ran around and asked strangers to pose with us in pictures. We went up to tourists and screamed, 'Where are you from?' "

Searching for the bank slip proved a major challenge for most teams. One team finally scored when one member, waiting to pry information from a museum guard, overheard a woman say she was in a hurry to find an exhibit because she had to catch a plane. The hunter immediately interrupted to ask, "Where is that plane going to?" Pay dirt: The answer was Texas.

The hunt also provided a chance, albeit fleeting, to see previously unexplored parts of the city. "I had not been to most of the places we went to," said Nancy Iovino, who recently moved to Georgetown from Connecticut. "We only had a few minutes to spend in the museums, but I am definitely going back to see some of the things we ran past."

"Our races give people the thrill of victory or the luxury of defeat," said Brad Mont, who organizes the races with his former college roommate Rich Von Riesen. "It is set up to be enjoyed by people who are very competitive, or by people who just want to have fun."

Hunters can do just about anything they want in the limo -- as long as it's legal and they don't make the driver break any traffic laws. The original concept didn't include limos, but Von Riesen said a 65-car race in San Diego was an eye-opener: "With that many cars all in a hurry to the same destinations, it looked like the movie "A Mad, Mad, Mad World." Luckily, no one got hurt."

The company's largest race was the January competition in Washington with 145 competitors and 24 limos. Washington's maximum is 200, not only to help the organizers but also to make life easier on museum guards, information desk personnel and storekeepers bombarded for answers or directions.

The keys, as the teams quickly discover, are using the few minutes between areas such as the monuments, Adams Morgan or the South Mall for planning and teamwork. One of the hunt's few rules is that use of the telephone is prohibited. Prizes are modest -- tickets to the Source Theater and bottles of champagne.

Amazing Adventures has organized hunts in cities such as Phoenix for companies that want to teach employees the benefits of working together. And "one of the best teams we ever had was a group practicing for an America's Cup yachting race," said Von Riesen. "They were just looking to do something for another exercise of teamwork."

If individuals or groups of fewer than six sign up, they're assigned to fill out limos of six before the race. Von Riesen said it's best if people with similar attitudes (competitors, say, or just fun-seekers) are matched with like-minded hunters. He takes credit for one perfect pairing: "In San Diego, a woman eight-and-a-half months pregnant signed up. I had the foresight to put her in a limo with a doctor. Sure enough, she went into labor in the middle of the hunt and the doctor helped with the delivery as the limo rushed to the hospital."

GREAT LIMOUSINE RACE -- This Saturday (then May 17, June 21 and July 19), noon to 5:30. Cost $36 per person. Registration must be in advance (credit cards can be used by phone) up to 6:30 p.m. before day of race. Call 966-9606.