The Washington Opera took a gamble with Gounod's "Rome'o et Juliette," the new production that opened its 1987-88 season. But Saturday night in the Kennedy Center Opera House, it looked as if the gamble was paying off. A capacity audience warmly applauded the vigorous young cast, not only during the prolonged curtain calls but also after many of the big numbers.

The applause was as much for the total production as for individual performers. Not many spoken plays receive the kind of illed and detailed attention that was lavished on this opera in its purely theatrical dimensions. Pasquale Grossi's splendid sets and David Roberts' opulent, evocative costumes provoked applause before a note was sung. Peter Mark Schifter's perceptive, energetic stage direction made this "Rome'o" a special experi ence from beginning to end, and the technical staff of the Washington Opera did its usual excellent work on such critical details as lighting and the text and timing of surtitles. Everything that technique and professionalism can do to make an opera work has been devoted to this production, and the positive effects are quite evident.

Still, there was a significant ri. Part of it lay in the choice of Gounod, who was once the hottest composer in the operatic repertoire (though more for "Faust" than for "Rome'o") but has slipped in the past generation to a position of respected semineglect. There was also ri in the choice of a young American cast to interpret this quintessential embodiment of a century-old French tradition. The opera's relative unfamiliarity (despite a Baltimore production last season) and the cast's relative youth are both epitomized by the fact that all the featured singers -- except for Marcus Haddock, the glowering, sinister Tybalt -- were singing "Rome'o et Juliette" for the first time.

This helps to explain the performance's freshness and vitality as well as the feeling that, on opening night, the singers had not yet reached their peak. Nobody was falling back on routine for this performance, because nobody had enough experience to develop cliche's in his or her role. At the same time, there was more than once a feeling of tentativeness, a sense that the singers did not yet fit into their roles with the complete comfort that would let them take little ris and stretch themselves beyond previous achievements. This is a cast that is still growing into its parts and that is likely to continue growing throughout the five remaining performances. But on opening night there was a carefulness in much of the singing that contrasted curiously with the physical vitality -- the boisterous teen-age spirit -- in much of the stage action.

Not that there was much wrong with the singing at this point in the production's development. Angela Maria Blasi, a Brooklyn native making her American debut after singing at La Scala, Salzburg and Covent Garden, was vocally radiant as Juliette, besides having a special bounce and spontaneity in her stage presence (notably in Act 1) that made her seem very much like the 14-year-old heroine. Tenor Neil Wilson took quite a while, on opening night, to slip into exactly the right vocal style. But after taming a slightly excessive vibrato (a sign of stress?), he sang superbly in Act 3 and part of Act 2.

Outstanding in supporting roles were several other singers also making their Washington Opera debuts: Haddock as Tybalt, Gloria Parker as Ste'phano, James Ramlet as the Duke, and particularly Gweneth Bean, an exquisite alto voice, as the nurse, Gertrude. John Fiorito is so well known to Washington audiences that it hardly seems necessary to mention that he sang with distinction in the role of Capulet. Other familiar performers living up to their usual high standards included James Busterud as Mercutio, Christopher King as Benvolio, and Jeffrey Wells as Fre`re Laurent. The chorus was well prepared and a vital element in the impact of the performance. And Cal Stewart Kellogg conducted with his usual expertise.

The opera itself is reasonably faithful to Shakespeare's original -- simpler in plot and character delineation, as musical theater has to be, and slightly "improved" in the final scene so that Romeo and Juliet can expire with one last duet. Compared with Shakespeare, Gounod and his librettists have perhaps more elegance and less vigor, but Schifter's stage direction, Elizabeth Keen's choreography and Jake Turner's vivid coaching of the fight scenes inject into this production a lot of vitality that is left at best implicit in the text.

This is, in sum, an expert and generally effective treatment of the opera and one that should improve as the singers come to feel more at ease with the Queen Mab aria, "Je veux vivre," "Ah! le`ve-toi soleil" and "Que fais-tu, blanche tourterelle.