SALT LAKE CITY (AP) _ Stop me if you've heard this one:

A fierce-looking man leads a Doberman into a New York hotel elevator already occupied by three women tourists. ''Sit, lady 3/8'' he barks - and all three women hit the floor.

''Lady'' is the dog's name; the dog owner is Reggie Jackson. He apologizes profusely and pays the women's hotel bill.

Did you hear about the muffin-lover who had a two-foot mass of undigested oat bran surgically removed from his intestines?

What about that poodle owner whose attempts to dry her newly bathed pet in a microwave had tragic - and messy - results?

Perhaps you've read some such story in a newspaper, or heard one told on a talk show. Maybe you've told one yourself. You may even know the poor schlep to whom such things keep happening: the ubiquitous Friend of a Friend (FOAF).

If so, a news flash: You've been had.

None of these stories is true, says Jan Harold Brunvand, a folklorist at the University of Utah who specializes in tracking and debunking ''urban legends.''

They're oral accounts of strange occurrences that are told as if true and often believed. Unlike myths, urban legends are set in the recent past and star normal humans rather than ancient gods.

Classic legends involve evil spells, monsters and treasure, and are set in haunted houses, cemeteries or horse-drawn carriages. Urban legends take place in shopping malls, suburban homes and cars, and feature Cabbage Patch Kids, blue jeans, and Michael Jackson albums.

Though it's tempting to think that some version of these events must have happened to somebody, Brunvand rather doubts it.

''For a folklorist, multiple versions from different places betray a story's oral circulation and variation,'' he says.

The New York dog owner comes in a variety of identities, Magic Johnson, Wilt Chamberlain, Eddie Murphy, O.J. Simpson, and Mean Joe Greene among them, although the Reggie Jackson version is by far the most popular.

(For the record, Reggie Jackson says he would never own a dog in New York. ''It would be cruel.'')

Though the story's details change, the basic elements remain constant: frightened white women, a supposedly threatening black man, and a dog. ''The strong emphasis on such themes probably shows how scared people really are, though in this story the fright is shown to be a foolish overreaction, and the black man is both genial and generous,'' Brunvand says.

In an older, British version of the elevator incident, a group of Americans touring Parliament obediently fall to their knees in a corridor when a costumed lawmaker strides by in pursuit of a colleague. ''Neil 3/8'' he shouts. ''Neil 3/8''

Urban legends often involve hearsay, but ''rumors tend to be relatively short-lived and non-narrative,'' Brunvand says.

''When a skilled storyteller begins to ask 'What if,' and when listeners respond, repeat the stories and add their own flourishes, legends begin to form and circulate.''

By the way, he reports, Coleco Industries does NOT issue death certificates for damaged Cabbage Patch dolls; nobody has EVER been crushed to death by shrink-to-fit jeans; and the first seven numbers in the product code on the ''Thriller'' album is NOT Michael Jackson's actual phone number.

In other startling non-news:

- A star-struck woman did NOT spot Paul Newman (or Tom Brokaw or Robert Redford or Jack Nicholson) in an ice cream shop and get so flustered that she wound up on the sidewalk sans cone. When she went back in to claim it, the aforementioned celebrity was NOT heard to say, ''You'll find it in your purse, ma'am - right where you left it.'' Joanne Woodward did NOT chuckle appreciatively.

- Little Mikey, the star of a Life cereal commercial, did NOT die of an exploding stomach after swallowing a handful of Pop Rocks and washing them down with soda. Just another pesky exploding-stomach legend, Brunvand says.

Who hasn't heard of the foolish young woman whose pursuit of the ultimate suntan led her to spend too many hours at the tanning salon? She finally sought medical advice after developing a nasty odor.

''Microwaved insides,'' diagnosed the doctor.

Half-baked, said Brunvand, who immediately recognized it as a distant cousin to the contact-lens-fused-to-the-cornea mishap stemming from a welding accident that never happened in Pittsburgh.

As the tanning salon story illustrates, urban legends do more than simply entertain. They also express fear - of technology, crime, contamination and other hazards of everyday life. ''Gruesome horror stories that take place in familiar surroundings are a staple of urban legendry,'' Brunvand says.

Some legends reinforce traditional women's roles with the dire consequences that result from serving the family contaminated fast food rather than home cooking, or from leaving the kids with the ever-popular Baby Sitter From Hell.

''Older stories based on baby sitter anxiety involved babies trapped in highchairs, or threatened by guard dogs or wild animals invading the nursery,'' says Brunvand. In newer versions, the danger is often posed by the sitter, a dangerously ditzy high school girl.

Though some basic storylines can be traced back decades or even centuries, the study of urban legends is relatively new. Brunvand's ''The Vanishing Hitchhiker,'' published in 1981, was the first book of its kind.

He intended it for the classroom, but a last-minute decision to add an appeal for more legends brought tons of mail, from armchair folklorists as well as students.

Realizing he was onto something, Brunvand followed up with three more books: ''The Choking Doberman,'' ''The Mexican Pet,'' and ''Curses 3/8 Broiled Again 3/8'' He also launched a weekly column, which runs in about 20 newspapers.

Urban legends have paid off the mortgage and put four young Brunvands through college, says the folklorist, who's in no danger of running out of material, even in these high-tech times.

''This folk process of oral transmission and transformation defies the march of progress. Folk tradition even hitchhikes along with technological advances. With computers, electronic mail and fax machines, there's all kinds of stuff being shot around.''

In fact, urban legends are so pervasive that you, too, can play folklorist. Just listen closely - and skeptically - to TV talk shows, garrulous neighbors and cocktail party chatter.

And heed the advice of a seasoned professional: ''Never trust a dead cat story,'' Brunvand says.