WITH BLACK TIE, big bands and Liberace in vogue these days, can ballroom dancing be far behind? Business at New York's Roseland Ballroom is booming, last month's Vanity Fair featured a cover shot of President and Mrs. Reagan tripping the light fantastic, and recently an eight- member troupe called American Ballroom Theater has been receiving rave reviews.

Founded by championship ballroom dancers Pierre Dulaine and Yvonne Marceau, American Ballroom Theater illuminates the art of "touch" dancing. One minute we're watching a routine a la Fred and Ginger, then a steamy tango, then a simple boy-meets-girl scenario. Even as we marvel at the sinuous patterns and dramatic lunges, it is the stories these steps tell that leave the strongest impression.

Choreographer John Roudis, a well-known dancer of the '30s whose career goes back to vaudeville days, has paid scrupulous attention to period detail. His dances, set to classic tunes, use the traditional steps of the fox trot, lindy, cha cha, rumba, mambo, tango and jitterbug, but he has woven these familiar routines into original pieces that play up the strengths of Ballroom Theater's four couples, who specialize in acrobatics, quick steps, sways and slides.

Ballroom dancing has always been enjoyed both as a participatory and spectator sport. After a dose of this group, members of the audience might just be inspired to float up the aisles in pairs.

AMERICAN BALLROOM THEATER -- Saturday at 8 p.m., Sunday at 4:30 p.m., Baird Auditorium, National Museum of Natural History, 10th and Constitution Avenue NW. Tickets $12. Call 357-3030.