"Ballroom dancing? Who, me? You've got to be kidding."

Like many of our friends in their early 30s, my husband and I have fallen into a kind of dance limbo: High-school hops are fast-fading memories; our disco days are definitely over; and the last big wedding we expect to be invited to was last summer. It's a long haul until we dance at our own children's weddings, so the long-term prospects seem pretty slim.

Not surprising, then, that a suggestion to go ballroom dancing drew an incredulous "I Won't Dance," don't ask me, from my husband; but duty prevailed and he ventured into the ballroom with me.

This area is a hotbed of ballroom dancing: The headquarters of the United States Amateur Ballroom Dancing Association is in McLean, the Mideastern chapter down the road in Arlington. This weekend the USABDA will hold its 17th Anniversary Ball and championship competition in Crystal City.

Roughly 2 million Americans regularly put on their dancing shoes to foxtrot, waltz, tango, quickstep, rhumba, cha cha cha, samba and jive. And about half a million of them take their dancing seriously enough to go to lessons on a regular basis, says Richard Mason, president of the USABDA.

For the real aficionados, dancing becomes a way of life. Washington's serious Freds and Gingers do most of their dancing at the social dances held by area studios. There's at least one dance every night of the week, except Monday. "On Mondays, they go to classes," says Mason.

Who's dancing up this storm? People over 40, for the most part, but the number of younger dancers is increasing, Mason says. "A lot of young people came in to learn advanced Latin dancing to incorporate Latin dance-styles into their disco routines," says Terry Gregory, owner of the THE FEATHER AND THREE DANCE STUDIO and a one-time U.S. Latin Champion. "But some of them got hooked on ballroom dancing along the way." At 8:30 on a Friday at The Feather and Three, just off Lee Highway at Harrison Street, Gregory mans the turntable that spins out big-band-era music and contemporary tunes set to ballroom tempos, while a revolving mirror-ball throws make-believe starlight around a long room with one wall of mirrors and three of stacking chairs. About 25 couples -- mostly older, but some in their 20s and 30s -- glide around the floor. The women, well-groomed and suburbanly chic, are dressed in everything from Danskin leotards with wraparound or flaring pleated skirts to one long dress and one sophisticated, ruffled black cocktail dress. At dance- floor level gold and silver high-heeled pumps skim the floor. The gentlemen wear shirts and slacks, with a debonair ascot or two in view. It is friendly and relaxed, but the emphasis is definitely on dancing, not chatting. Many are in the same studio class and have come to practice together, Gregory says. Sunday nights are the big social evenings, when 150 people show up for the open-to- the-public buffet dance. "There are more singles on Sundays," says Gregory,"but they come here mainly to dance, not to get picked up." Still, many a romance has blossomed from a quickstep pairing: Three of the couples here tonight waltzed from the ballroom floor on down the aisle. The music switches from an up-tempo quickstep -- which had the dancers flying past in athletic hops, skips and jumps -- to a staccato tango, the international version: clipped, formal with sudden stops and turnabouts and a curious henpeck neck action. Gregory puts on a swing record and I'm asked to dance. I try to follow my partner's lead but end up, red-faced, receiving an impromptu lesson: Side together, side together, one, two. . . My husband politely, but flatly, refuses a similar invitation from a woman: "I'm just the chauffeur," he explains. Waltz time. From the sidelines we watch enviously as backs straighten, leg person. s swing out with toes pointed and the dancers swoop and swirl around the floor. "They're certainly enjoying themselves," admits my husband. For a few moments, the shopping- plaza dance studio is transformed into a chandeliered Viennese ballroom. Over at THE MARQUEE LOUNGE in the Shoreham Hotel, we find a make-believe ballroom that's born-again Art Deco down to its swizzle-stick logo, Busby Berkeley on a smaller scale. Sculptured ceiling cove moldings hover like clouds over a room awash in shades of sea green and dark blue. The two-tiered seating includes oversize padded banquettes against the walls, clusters of tables and a row of tall marble-topped tables with stools. There's also a curved, mirrored bar off to one side. Lalique-like lotus lamps flicker on the tables. Waiters and waitresses in smart, braided bellhop outfits reminiscent of the Phillip Morris pageboy step up briskly to take your order. Tracklighting choreographed to change hues with the music's moods completes the sound-stage set, which is pure glamor simply begging for Astaire and Rogers to sweep into the spotlight. Mike Crotty's 10-piece orchestra is warming up the almost-capacity Friday-night house with first-class, solid big-band music. Silk dresses and well-tailored linen suits drape the ladies, though there's one exquisite long gown of gray moir,e. Navy double- breasted jackets with cream or white pants seem de rigeur for the gentlemen, but a tuxedo is squiring the moir,e gown. It's a mixed crowd: some convention holdovers, some anniversary-dinner couples but -- surprise -- quite a few couples in their 30s. A fast number brings a good crowd onto the floor and triggers an assortment of styles that reflect definite generation gaps: '40s jitterbugging, '50s rock'n'rolling and '60s free- form shuffling. The band switches to a hotblooded rhumba and the fainthearted flee to the safety of shadowy tables, leaving the floor to three very young couples who swivel through well-practiced routines. The first sliding notes of "A Sentimental Journey" bring out most of the older couples. A look at their dreamy-eyed faces seems to tell us they're taking that journey tonight. Then everyone gets up for "My Foolish Heart," as the dance floor darkens, granting anonymity. The lights come up and the band heats up for the 40-minute set's last number. Just about everyone stays on the floor and whoops it up at "A Woodchopper's Ball," as the band rises to its feet for the finale. Even if you don't dance -- we didn't -- this room offers great music (played as it should be in a large room with good acoustics), lots of glamor and some of the best people-watching around. This evening, a silver-haired leprechaun in navy blazer and white pants, but dancing in a rubber-legged style reminiscent of Cagney's Cohan, is enjoying himself immensely; a tall, slim, very swish couple takes to the floor -- he silk-suited and glumly handsome, like a TV anchorman (or a henchman, my husband less kindly suggests), she a vision of frothy white in a shoulderless dress of ruffled-and-tiered white gauze, her explosion of blond curls kept in check by a flapper's headband above an expertly made-up and neutral face -- high-fashion mannequin or gun moll? The bill: $7.50 with tip for two drinks, free peanuts and an hour's entertainment. "This is a great deal," says my husband. "We're definitely coming back here -- when I'm in a dancing mood." At the TOP O' THE TOWN in Arlington, a glass-walled elevator whisks you up to a penthouse nightspot spectacularly overlooking the Potomac: The Washington Monument seems to stand atop the Lincoln Memorial, as planes flicker past (unheard) like mammoth fireflies; carlights twinkle enough to maneuver your partner's back toward the picture windows, you can keep the sparkling view in sight while you swing and sway. Entertaining this slow August evening (and every Wednesday) is Jackie and her (nine-piece) Orchestra. Jackie is Jackie Schmitt, also heard around town as one- fifth of the Foggy Bottom Five. She's a snazzy, jazzy lady with a big voice that soars on the up-beat numbers and swoops to a throaty, mellow low on the slow tunes. Her rendition of "When Sunny Gets Blue," complemented by Don New's cool tenor sax, completely takes your mind off the view. On Sunday nights, Trux Baldwin and his 17-piece Starlite Orchestra take over the bandstand from 8 to 12. There's a $4 cover Sunday night, $3 Wednesday. Drinks for two, with complimentary hors d'oeuvres left over from the 4 to 7 happy hour, came to $5.25. It's eerie, late on a Sunday night, to walk up from the pitch-black parking lot to the SPANISH BALLROOM in the ghost town of Glen Echo Park, but a glimmer of light leaks from a hulk to the right of the shuttered carousel, and faint strains of "Moonlight Serenade" compete with the chorus of frogs and crickets. Inside, the rich and reedy sound of Frankie Condon's big band is reverberating in the vast ballroom -- the first big-band music here in 23 years, says Condon. The band is framed by a blue stage with "Glen Echo Park Crystal Ballroom" bold across the backdrop of a star-spangled sky, the few gaping holes looking like black holes in this make-believe galaxy. Toni Rae steps up to the microphone to warble a bouncy "Lullaby of Birdland" and exactly 26 couples -- mostly casually dressed -- take to the floor. We -- yes, we have finally succumbed to the faded romance of this dance palace -- are slightly overwhelmed by the expanse of the pseudo- Spanish hall with its a-little-worse-for-wear Moorish balconies and boarded-up clerestory windows. Most of the dancers won't see 40 again but a few younger couples have staked out turf in the corners to practice newly learned steps. On the old oak waiting- room chairs, only a few of the 80 or so people here tonight sit to watch or listen. The music's echoes evoke the ghosts of dancers past who used to swell the cheek-to- cheek Saturday-night throngs. "It's a nostalgia thing," says Frankie Condon, "and we're having a lot of fun." A little past 10:30, the band bids us goodnight with their theme song, "Showpiece." They'll be back next Sunday and every Sunday until September 26 (the ballroom isn't heated) from 7:30 to 10:30. Admission is $3. LIVE AT CRYSTAL CITY You can watch the best amateur ballroom dancers in the country strut their stuff this weekend at the Marriott Gateway Hotel Ballroom in Crystal City. On Saturday, 11-5 (tickets $7), and Sunday, 11-3 ($10), they'll be competing for the USABDA Championship titles and giving demonstrations. If you want to take to the dance floor yourself, join USABDA members at their dinner dance Saturday night, $25 or $10 for dancing only. Call Connie Townsend, 301-539-0872 (days), 301-821-8784 (evenings). SHALL WE DANCE? Here's a partial list of local spots where you can dance in "The Old-Fashioned Way." THE MARQUEE LOUNGE -- Shoreham Hotel, Calvert Street and Connecticut Avenue NW. Dancing to live music Tues. to Thurs., 4:30 to 1; Fri. and Sat., 5 to 2. No cover; jacket and tie. Reservations taken only for hotel diners. 234-0700. TOP O' THE TOWN -- 14th and North Oak streets in Arlington, directly behind the Iwo Jima Memorial. Dancing to live orchestra on Wednesdays ($3 cover) and Sundays ($4), 8 to 12. 525-9200. SPANISH BALLROOM -- Glen Ech dinner. Jacket and tie. Call 587-5400. CAPTAIN WHITE'S -- 8123 Georgia Avenue, Silver Spring. Big-band dancing Tuesday and Thursday nights. Call 589-6868. TEA DANCES -- Both the Gaithersburg Marriott, 9079 Shady Grove Road, (977-8900), and the Capitol Hill Hyatt Regency, 400 New Jersey Avenue NW (737-1234), will resume ballroom tea dances in September. THE FEATHER AND THREE DANCE STUDIO -- 2433-A North Harrison Street, Arlington. 538-4663. DANCELAND II -- 5207 Wisconsin Avenue NW. 363- 8344. JOE JENKIN'S DANCE STUDIO -- 5017 Wilson Lane, Bethesda. 986-1363. STUDIO ONE -- 8743 Cooper Road, Alexandria. 780-1800. ATWOOD'S DANCE CLUB -- 10528 St.Paul Street, Kensington, Md. 946-0252.