The Joffrey Ballet got off to a grand start last night for its two-week visit to the Kennedy Center Opera House by the simple expedient of beginning with its all-Ashton program. The Ashton ballets the company has acquired over the years constitute one of the brightest sectors of the repertory, all the more so because no other American troupe has as much of his work.

The evening, indeed, was billed as a "Salute to Sir Frederick Ashton," honoring the great British choreographer in his 80th year. The four ballets of the program -- as small a sampling as that may be compared to Ashton's prodigious output as a whole -- attested both to his scarcely rivaled mastery of the classical tradition and to the awesome range of theme and mode he achieved by extrapolating from that tradition as a base.

"Monotones II," created in 1965 to orchestrated versions of Erik Satie's "Trois Gymnopedies," presents Ashton's classicism in its purest form, stripped to barest essence, an abstract play of balletic line and artful geometry. It's too bad, in a way, that the performance of this particular work was the weakest of the evening, because it is just this kind of poetic formalism that lies beneath the graces, conceits and drama of all other Ashton ballets.

The magic of "Monotones II," precisely by reason of its pristine, unadorned quality, is exceedingly fragile, and last night's trio of interpreters -- Patricia Miller, Glenn Edgerton and Tom Mossbrucker -- simply failed to capture it. Above all, the choreography, its celestial stillness matching the tranquil poise of Satie's music, requires a strictness of placement and an unbroken, fluid serenity. Last night's cast was too fussy in articulation and not precise enough in ensemble to sustain the spell.

Much closer to the mark, though still short of the Joffrey's highest standards, was the opening "Les Patineurs," Ashton's ever-popular gloss on ice-skating, set to the buoyant tunes of Meyerbeer. The delightful park-in-the-woods scenery, constructed after William Chappell's inspired original designs, and the equally charming costumes were as much of an advantage as ever. And in this case, ensemble was a strong point -- the cast danced the ballet as if it owned the patent. There were some standout individual passages as well -- the sweetly amorous duet by Denise Jackson and Philip Jerry, for example. But Carl Corry, substituting for an ailing Mark Goldweber, didn't quite come up with the dazzle one looks for from the Boy in Blue, and several other variations were too much on the hectic side. Carole Valleskey's fouettes, on the other hand, were brilliance itself.

The company was at its sterling best in the two more distinctly offbeat and dramatic ballets of the program -- the surreal "Illuminations" and the slyly comedic "A Wedding Bouquet." Luis Perez was profoundly impressive as the erratic, visionary Poet of "Illuminations," a ballet originally created for the New York City Ballet in 1950 to a score by Benjamin Britten. The French text of Britten's music, persuasively sung last night by tenor David Britton, consists of poetry by Arthur Rimbaud, and it is Rimbaud's life and fevered imagination that this still daring work attempts to evoke. There's no story line, just a series of dreamlike scenes peopled by creatures of the Poet's brain, rendered ever so fantastic in semblance by Cecil Beaton's setting and costumes. Matching Perez in intensity of characterization, and contributing a special sensual charge of her own, was Beatriz Rodriguez as Profane Love.

Rodriguez was superb also as the demented Julia in "A Wedding Bouquet," a part created by Margot Fonteyn in the original English production of 1937. This giddy but understated farce, depicting a French provincial nuptial party at the turn of the present century, needs an extremely deft and subtle histrionic touch, and last night's Joffrey cast had it just right.

The narrator, who reads selections from Gertrude Stein chosen by composer Lord Berners to go with his dryly bouncing score, must combine humor, waspishness and crisp declamation -- Grayson Hirst, last night, showed us just how to best the challenge. Also on target were Carole Valleskey as the vivacious maid, Webster; Luis Perez as the supercilious Bridegroom; Dawn Caccamo as his blithely naive Bride; Charlene Gehm as the besotted guest Josephine; and Tina LeBlanc as Julia's frisky terrier, Pepe.