FIRST IT was Vernon and Irene Castle. Then it was Fred Astaire and Ginger Rogers. And now, could it just be David Martin and Keiko Moore?

Martin and Moore? Though this local dance duo may not yet have achieved the status of their fleet-footed predecessors, the pair's exquisite renditions of the cha cha, rumba, jive and other Latin-style routines have catapulted them into the ballroom big time: the World Amateur Ballroom Championships, held this weekend in Stuggart, Germany. Sponsored by the United States Amateur Ballroom Dancers Association (USABDA,) Martin and Moore are one of only two couples representing this country in an annual competition that attracts contestants from over 20 nations, and patterns itself after the Winter Olympics' figure skating events.

As far as parterships go, you couldn't find a more contrasting pair. Born in Tokyo, soft-spoken, ultra-refined Keiko Haratsuka Moore practices and teaches the traditional Japanese arts of woodblock printmaking and brush painting, draws elaborate illustrations of fish for the National Marine Fisheries Service, and even designs and sews her meticulously sequined and feathered ballroom dresses. Though she looks about 20 on the dance floor, Moore is the mother of four grown daughters.

Her partner is quite another story. A blond, mustachioed fellow with a boisterous sense of humor, David Martin was born here in Washington and grew up in Laytonsville, Md. Age 33 and single, he works as a computer programmer (often the night shift, which plays havoc with rehearsal time) at NIH, and loves to tinker with mechanical things like automobiles and model airplanes.

How, you might ask, did two such disparate folk become a serious dance team? About five years ago Martin and Moore met as students at the Atwood studios in Kensington. Neither had taken dance as children. Martin had been attracted to ballroom classes for social reasons, and for Moore it proved a kind of thereapy ("You forget all your problems when you're dancing," she says).

Encouraged by their instructor, the two joined forces; seven lessons later, they won second place in a novice competition. Since then, they've entered three regional competitions a year, taken scores of private lessons from former champs Beverly Donahue, Al Frantz and Nancy Jenkins, plunked down $2 time and again in order to reserve rehearsal space at local studios, and attended countless social gatherings so as to better their routines and practice propelling themselves through an aggressive crowd.

Watching Martin and Moore go through their paces, it's easy to understand why they've done so well, and why the art of ballroom dancing is currently enjoying a comeback. They're a diminutive, feisty pair, equally gifted in both the modern (waltz, fox trot, tango, quickstep) and Latin (cha cha, rumba, paso deble, samba, jive) styles. Their jive (alias Lindy Hop) is full of dramatic poses, scuttling little runs and skips across the floor, labyrinthian armwork that always seems to come out just right. The dancers move wonderfully together, then break into individual displays. Moore extends her leg in a languid arabesque while Martin spins blithely on his well-oiled knees.

"The paso doble is David's favorite because he can show off," laughs Moore. In this dance, Martin plays a matador, Moore his malleable cape. Dressed in a catsuit -- a one-piece, body-hugging tuxedo with sequins down the seams -- he flies through the air, turns and slides wildly and the human cape, a stunning vision in her green silk and sequins, goes whirling rapidly away. Their cha cha, too, is something special -- a flirtatious romp composed of many subtle undulations, knowing glances and sudden freezes.

Sitting in on a last-minute lesson, one observes that both dancers are perfectionists. "I'm not satisfied with my product yet," Martin explains. The fact that he's partially deaf does not deter him, either; his sense of rhythm, especially in the Latin numbers, is impeccable, and he's constantly working to improve his shoulders, his head, his facial expression.

Moore has her frustrations too. "It's a disadvantage to be short," she declares. "We have to be twice as good to be noticed by the judges . . . And there's no place to practice. Studios don't want amateurs coming in during classes." And of course there are money problems. To finance their overseas trips, the team has performed at USABDA benefits, and rejoice at their German hosts' gift of one free night of room and board.

Will Martin and Moore take the plunge and go professional? It's too early to tell; in fact, the two are still recovering from the shock of having been chosen for this current competition. "We might have had expectations, but we never dreamed we'd come this far." Moore smiles impishly. "Dancing is my hobby right now. But who knows? It may become more than that!"