the opening ball scene in "Rigoletto." But the wine and the food were real.

It was the 1985 Washington Opera Ball at Firenze House, the magnificent residence of the Italian ambassadors here, and the people, the costumes and the setting were worthy of Milan's great opera house. Before last night's ball, 400 select guests had started their evening with dinners at 28 embassies.

As Swedish Ambassador Wilhelm Wachtmeister put it, toasting the 26 dinner guests at his embassy, "It is an unusual evening because we did not pick our guests, nor did our guests pick us. Even so, I do not think that we could have had a pleasanter company."

The ball is a favorite of Washington embassies, so the evening is always heavy with international glamor. A number of people last night swept over to meet Anna Bulgari, the wife of Nicola Bulgari, so they could see what the famous jeweler had presented to his wife. Her necklace and matching earrings were made of emeralds, pearls, rubies and diamonds.

"I collect prewar Buicks. I admire American automobiles before 1930 and I think the jewelry made in America from 1890 to 1940 is some of the best designed and executed ever," said Bulgari, the third generation of the Italian jewelry family.

Catherine Stevens was this year's ball chairman, and she and her husband, Alaska Sen. Ted Stevens, dined before the ball at the Ritz Carlton, which along with the Four Seasons gave a before-the-ball dinner.

Tickets began at $300 each and went up to $1,000 each for sponsors. One of the ball's biggest contributors was the Shaklee Corp., the cosmetics and health company, at $25,000. There were also donations from 61 other corporations.

"We tried to reach out to the corporate world nationally because Washington just doesn't have enough corporations to support the opera," said Catherine Stevens. Added Paula Jeffries, chairman of the Washington Opera Women's Committee, "We made at least $200,000 from the ball. This is our single biggest benefit."

At Firenze House, presided over by Italian Ambassador Rinaldo Petrignani and his wife Anne Merete, ball-goers gathered in the three-story high Great Hall with its sweeping staircase and elaborate contemporary Italian art. Outside, for protection against the June showers, Woodward & Lothrop provided white tents, where Renaissance lilies seemed to grow in profusion.

The guests were greeted by "supers" in costumes from the Washington Opera's productions of Bellini's "La Sonnambula" and Donizetti's "L'Elisir d'amore." Musicians playing recorders and other antique instruments appropriate to the hall provided the accompaniment to the guests entrances.

Waiters with champagne in fluted glasses greeted the guests as they came from the receiving line. Defense Secretary Caspar Weinberger and his wife Jane, out on the terrace, compared notes on their dinners with writer and socialite Ina Ginsburg. "The food was out of this world at the Brazilian Embassy," said Ginsburg, "from lobster mousse to crepe Copacabana."

The Weinbergers had been at the British Embassy for sole, veal, artichokes and asparagus finished off with an appropriate dessert -- the floating island. Lady Marjory Wright, wife of the British ambassador, eating one of the fancy ice cream sundaes offered on the terrace, said, "You can see I didn't think so much of my food."

At the Swedish Embassy, where Countess Ulla Wachtmeister is praised for her table settings as well as her food, the fish course came in abalone shells to match the shell decorations on the table. The most unusual course was reindeer.

The ball, one of Washington's latest evenings, ended well after 1 a.m. As Wachtmeister -- who has been here 11 years and 1 month -- said, "My diplomatic life in Washington is possible because most evenings end at 11 o'clock."

But last night, the Wachtmeisters, the Petrignanis, Rep. Claude Pepper and Frances Humphrey Howard were among the last on the dance floor.