Holler down a taxi in Washington and Mary McCullough may purr up in her loveboat of a cab - endless gleaming feet of turquoise Cadillac Sedan de Ville with a gold running strip, a hint of tail fins, aqua leather upholstery, clusters of paper daisies and roses in the rear window, and a license plate that reads ''Very Important Woman'' just below the numbers.
Ms. McCullough is cabbie to the stars. And she wants them to ride in the style to which they've become accustomed. So far she's hacked, Cadillac style, for a dazzling list of fares: Lilli Palmer, James Mason, Helen Hayes, Judith Anderson, Claudette Colbert, Eartha Kitt, Anne Jackson, Eli Wallach, Jean Stapleton, Peter Falk, Michael Moriarty, Carol Channing, and Jennifer Holliday.
It all started one cold night in 1976 when she pulled up in front of the National Theatre, where ''Same Time, Next Year'' had just opened. Instead of a suburban couple bound for Gaithersburg, in suburban Maryland, her fares turned out to be Barbara Rush and Tom Troupe, the stars of the play. They enjoyed their ride with Mary (a real theater buff) so much they asked her for an encore. Would she be willing to pick them up before and after each performance for the run of the show?
Would Elizabeth Taylor like a diamond mine? Would Art Buchwald like to win at Wimbledon? Don't ask.
She was off and rolling in new territory. Kennedy Center, which shuttles its share of stars in and out of Washington, heard about her. Since 1976 she's been on call there for star rides, through a beeper system. She's also on tap at Ford's Theatre, the Warner Theater, the National, and, once a year, for a special contingent of DAR ladies. ''They be blowing their horns,'' she says of the other taxis when she rolls to the head of the line, ''but the DAR ladies say , 'This is a special driver.' ''
Tiki Davies, a spokesman for Kennedy Center, where Ms. McCullough is a backstage byword, says, ''How did you find out about Mary? She's fabulous. She's chipper and funny and wonderfully calm and cheerful all the time. The performers all love her. Mary's very proprietary about her stars. She drives carefully, doesn't scare anyone to death like some drivers.''
Mary McCullough says she's been in the taxi business for 27 years, ''but the last eight years have been the best, since I've been able to be with special people, to carry them around. I love 'em all.''
She is a warm, ample black woman with a headful of curls and a long, sweet smile. For driving, she wears comfortable duds: a tunic blouse of blue and lavender stripes, black skirt, tan lace-up shoes. Around her neck hangs a large gold key, containing pictures of her two godchildren.
She pulls up in her Caddie cab for our interview and steps out carrying a large roll of ruby oilcloth. When it's unwound, it turns out to be several feet of mounted, autographed playbills and photos from her star turns: James Mason and his wife, Clarissa Kaye, appearing at Kennedy Center in ''Partridge in a Pear Tree,'' and writing ''To our wonderful Mary McCullough, our gracious and best driver, Clarissa and James.'' And Donald O'Connor, tooling back and forth to ''Showboat,'' writing ''To Mary, You're Wonderful.'' Or ferrying the entire cast of ''Morning's at Seven,'' Maureen O'Sullivan, Kate Reid, Elizabeth Wilson, and Teresa Wright, at the National.
At the same time she drove Judith Anderson to her nightly destruction as ''Medea'' at the Kennedy Center. The voice of Dame Judith rolls in deep, dramatic tones across the phone from Santa Barbara, Calif.: ''Yes, I remember Mary well. She was very prompt, and sometimes had her dear little godchild with her. She was a reliable and excellent driver.'' They didn't chat a great deal, adds Dame Judith.
It was a bit more antic taxiing various ''Annies'' (but not their dogs), and at least two Miss Hannigans. And picking up the tape of a crucial NBA playoff for grateful basketball fan Peter Falk, who was starring in ''Make and Break.''
Ms. McCullough has seen as much theater here as some professional critics, because, along with the fares, checks, and occasional gifts, often come complimentary tickets: ''Guys and Dolls,'' ''Twice Around the Park,'' ''The Late Christopher Bean,'' ''Daddy Goodness,'' ''Whose Life Is It, Anyway?'' ''Room Service,'' ''Purlie,'' ''Bubbling Brown Sugar,'' ''Hello, Dolly!,'' ''Your Arm's Too Short to Box With God.'' She carried several of the stars for that one, and ended up inviting the whole cast back to her apartment for a buffet of soul food and health food.
Some of her stars have also become friends, like Lilli Palmer, who appeared here in ''Sarah in America,'' the one-woman show on Sarah Bernhardt. ''She told me she wanted me to have something to remember her by,'' Ms. McCullough says. ''I was carrying a little old case, and she gave me a Gucci shoulder purse, a scarf, and a wall tapestry,'' before the star went back to her home in Switzerland.
When Ms. McCullough first started carrying stars, she was driving a little Plymouth. She has traded up until she reached the semisplendor of her present ' 76 Cadillac. But she's not through yet. ''She's upgrading,'' says Tiki Davies. ''She really wants a Swedish Volvo limousine, the one that's only for ambassadors. She calls the Swedish Embassy every so often to see if she can buy the ambassador's old car, She feels that would be the best way to drive her stars.''
She lives simply, this woman who left her trade of cleaning and pressing to try hacking in 1956. ''Everyone said it was too dangerous for a woman then,'' she recalls, ''but I use my discretion.'' She says she's been well protected: ''I always say the Man Upstairs watches over me.'' She has also taken courses on radio at a local school, been a disc jockey on a Washington radio station, had her own gospel music program, done charity work, and been a member of the city Hackers' Board.
As a driver, she delivers a bit more than she's expected to. When Hal Linden appeared on the Washington TV talk show ''Morning Beat,'' a woman in the audience popped up and said, ''I saw you in 'Room Service' and thought you were splendid.'' A startled but grateful Linden climbed into the cab after the program and said, ''Thanks, Mary. That was my kind of personal publicity.''