Perhaps you've heard of them. Perhaps you've actually seen them jogging through the neighborhood in their motley running gear, shattering the suburban calm with their hunting horn and cries of "On, on!" and "Checking!" One moment they're here -- peering down alleys, scaring the dogs and otherwise distribing the peace -- and the next moment they're gone.Was it real, or a nightmare vision brought on by too many beer and soft-drink commercials?

Unlike the Flying Dutchman andhis ghostly crew, the Hash House Harriers do exist -- unfortunately, some might say. They seem to be most visible on Monday evenings during the warmer months of the year, but they can also be seen on Saturday afternoons in the fall and winter. Just when you've looked up from your lawnmower to ask. "What is this, a marathon?" they have vanished.

But the stares and questions simply add to the fun of hashing, a sport once described as "jogging run amok." If you liked playing kick the can on warm summer nights as a kid, and you can run five or six miles as an adult, hashing may be the sport for you.

Hashing in the 1980s version of the time-honored English schoolboy game of hare and hounds. One runner, designated the "hare," lays a trail marked with flour that his companions, "the hounds" then follow in pursuit. Numerous false trails complicate the chase,which ends at a keg of beer or other source of fluid replenishment.

But outlining the rules does not convey the true flavor of hashing. The trail can go anywhere: through parkland and froest, along railroad tracks, across streams, even into buildings. Local hashmen recall the day the flour led through the Grand Foyer of the Kennedy Center, leaving Saturday matinee-goers agape as the sweaty pack of human hounds passed through their midst.

Another time an inspired hare laid a trail through the National Zoo after closing hours. As the Park Police closed in on the hounds, the Americans in the pack, invoking emergency procedures, sprinted for cover, leaving foreign members with diplomatic immunity behind to negotiate with the law.

"We all started speaking Hungarian," one hashman recalls.

In short, a well-planned hash is an adventure and a treat in addition to being a good workout -- which explains why the sport has spread around the globe since its modest birth some 40 years ago. Hashing had its origins in Kuala Lumpur, Malaysia, in 1938 when an Australian named A.S.Gispert began jogging on Monday nights to sweat off the excesses of preceding weekends. He was joined by other expatriates seeking to "take the curse off Mondays," as hashmen put it, and the group repaired to a Chinese eatery known as the Hash House folling their runs.

As the runners began exploring different routes around the Malaysian countryside, the Hash House's enterprising proprietor arranged to meet them at the finish with a beer wagon. Overcome with gratitude, the Hash House Harriers named their club for his establishment.

Gispert died in the Battle of Singapore, but the club was revived after World War II by another Australian, who successfully claimed war reparations to replace 24 missing beer mugs and the club's battered bugle. One member started an affiliated club in Singapore, and other branches quickly followed.

The Washington Hash, which celebrated its 400th run in May, was begun by Bill Panton, a World Bank agronomist who had been a member of the "Mother Hash" in Kuala Lumpur. Panton collected five friends for the first event in 1972. Since then the club has grown to exceed 100 members, and several former members have dispersed like spores, to start chapters in other cities at home and aboard.

Each week members receive a circular containing directions to the next event, a "reHash" of the previous week's run, and a compendium of off-color jokes and trivia ("Hash Trash"). Each member is expected to serve periodically as hare, laying the trail and providing apres hash refreshments for the 30-odd members likely to show up for a meeting.

There is a low-key rivalry among the hares to outdo one another at the apres hash. Perhaps the most memorable was the summer night in rural Fairfax County when goggle-eyed hounds were greeted with a scene approximating Paradise: a torch-lit clearing with two sarong-clad Polynesian maidens (in truth, exercise instructors recruited from a local health club) who embraced each finisher and decorated him with a plastic lei.

As might be suspected, the Hash is a resolutely male chauvist organization.

A dog-eared club rulebook prohibits gambling, opium smoking and "the introduction of females and bad characters on runs." Unlike some Hash chapters, which have succumbed to pressures to go co-ed, the Washington club directs interested women runners to a counterpart organization, the Hash House Harriets.

The Harriettes, for their part, haven't responded in kind. "We thought about excluding men from our runs," said one member, "but they have nice legs so we decided they could stay."

The rules of hashing are simple, and almost any group of runners can learn to play. Limited vocabulary, limited competitiveness and even limted intelligence present no obstacles to hashing, as they do to most other human endeavors. The club motto says it best: "If you've half a mind to join the hash, that's all you need."

The key to a successful run is the hare, who must spend some time and effort planning the course and marking it with flour. A good run rarely covers less than four miles or more than six; even seasoned hashmen will complain if the run takes more than an hour.

Having plotted his course,the hare marks it with spots of flour every 50 yards or so. At intervals of about a half-mile, or at obvious junctions, he should draw a flour-marked "x," known in hash parlance as a "check" designed to halt the pursuing hounds. A check shoud present the hounds with some guesswork, since the trail can then lead in any direction -- forward, backward or to the sides. Within 200 yards of the check, the hare resumes the trail of flour spots.

Clever checks are considered essential to a successful hash; they bring an element of luck and skill to an otherwise predictable cross-country run. The checks also enable less fit runners ("Tail-End Charlies") to catch up with the leaders.A skilled hare will plan several "back checks" detours that trick strong runners into pursuing false leads while the laggards find themselves near the proper trail.

While the hare's role is the most difficult, there is also an etiquette for the hounds. The leader who finds the flour trail shouts, "On, on!" and the other hounds repeat the phrase. On reaching a checkmark, the leaderr yells, "Checking!" This word is repeated until someone finds the trail again, where upon a resounding chorus of "On,on!" signals the renewed pursuit.

Although the Washington club includes a fair number of serious runners, hash etiquette frowns on competition. No one cares who comes in first. In fact, hashmen profess a perverse admiration for SCBs ("short-cutting bastards") who can find the beer without running the full trail. Rosie Ruiz would be welcome -- if she weren't female.