"These Viennese women! They are dangerous!" is one line in "Wiener Blut," the last operetta by Johann Strauss the Second. "Seductive, elusive, mysterious" are other labels that could as well be added after seeing the Washington Opera's gorgeous new production that opened in the Kennedy Center on Christmas night. It is scheduled for nine more performances between now and Jan. 1.

It is somewhat misleading to speak of "Wiener Blut" as being by Strauss, who died five months before its premiere in October of 1899. But even before his final, fatal bout with pneumonia, Strauss had taken a hand in choosing those of his melodies which would be used in the new score. He had also given permission for his colleague, Adolph Muller Jr., to make the necessary musical arrangements. That the final result bears comparison with Strauss' own "Fledermaus" and "Gypsy Baron" speaks well indeed for Muller's work.

The title of the piece is contained in the line of dialogue that asks "Does one gain strength from Vienna blood?" The answer could be that both strength and that indefinable, intangible yet unmistakable quality the world knows as Viennese can be heard and felt in much of this music. The musical spirit of Johann Strauss, the Waltz King, is, in many ways, the most subtle, tricky, and hard to capture in the world. The same is true of the underlying mood of his operettas.

The Washington Opera production succeeds visually with ravishing sets and costumes by Zack Brown, who has now put four widely differing operas on the Terrace Theater stage in a manner not to be surpassed. His backdrop and elegant sets suggest Vienna in 1815 while his lavish costumes recreate the luxuriant frivolity of the wildly mixed-up story of mistaken identities. The gardened gazebo in the last act is magical. With lighting by Christine Wopat and the makeup and wigs of Charles Elsen, this "Wiener Blut" is a delight for any eye.

The score has some wonderful ensembles in which various pairings of the six principals, often heard above the chorus, create considerable excitement. These came off well, though without the kind of buildup that is possible and desirable. The six principals look and move easily through the make-believe romance, and the women sing handsomely. Janice Hall as the dancer, Cagliari, brings a lovely voice and manner to the role, sprinkling it generously with the kind of minxish quality it needs. Equally attractive in sound and style is Joy Langton's Pepi. She keeps the part on a high artistic level at the very same time she fills it with a saucy pertness. aKaren Hunt sings the Countess Gabriele very well from a purely vocal standpoint. What the role needs is a far wider range of light and shadow in sound that continually suggests that seduction is just around the corner. Every one of the women could greatly enhance their portraits by intensifying this element, which is the soul of Viennese operetta.

The three men are strangely unsatisfying. Warren Ellsworth's tenor is undisciplined and raw in sound, with no change in texture or delivery at any point. David Rae Smith works well dramatically but with a tired sound. As Josef, the valet, Russ Thacker is much more American than Viennese in his comedy routines. And he is not helped by far too frequent repetitions of the line "And that's a fact," which wears out its thin welcome early in the show.

Hugh Wolff is making his debut as an opera conductor with "Wiener Blut," an assignment veteran conductors might fear. He holds it together well, but there is missing from both singers and conductor that constant flexibility, that holding back of a crucial note, that mysterious quality -- hard to achieve -- that marks a great performance of a Viennese operetta. The chorus sings very well and handles its special assignments in dancing and movement with polish, to which is added attractive ballet. The orchestra sounds grainy where it should sound like silk shot with gold.