Reprinted from yesterday's late editions.

Since 1961, when the United States and Cuba severed diplomatic relations, the once elegant old mansion on 16th Street that used to house the Cuban Embassy has stood empty and decaying.

But last September the two nations ended their almost 17-year diplomatic break by establising "interests" sections in each other's capital to represent them.

And Monday night the Cubans once again opened the mansion to social Washington. The occasion was a cocktail and buffet reception celebrating Cuba's National Day - Jan. 1.

"Actually, we are a little late," said Ramon Sanchez-Parodi, who heads the Cuban Interests Section here, technically a part of the Czechoslovakian Embassy."Jan. 1 is the actual anniversary of the triumph of the revolution, but we had many things to do to the building after 17 years of disuse. So it took time.

"Will we be doing much entertaining? Probably. You have to do it. It is part of the Washington life."

Before the 1959 Cuban revolution, Cuba's connection with Washington life was snazzy indeed. Rated then as one of the most glamorous and prestigious of embassies, it was noted for its moonlight garden parties, rhumba music and fine food.

And Monday night even though things have changed considerably since - it was still clear that they love a good time.

The mansion itself looks spectacular once again, with a marble staircase leading to the upper levels newly refurbished with paint, carpeting and lights. An estimated 300 guests wandered through ordering Cuba libres at the bar and helping themselves to a sumptuous if predictable diplomatic buffet of roast beef, sliced turkey, cheeses and fruits.

The guest list - some political than social - included Deputy Assistant Secretary of State Mark Schneider, presidential assistant Peter Bourne and his eife, Mary King, deputy director of Action, former Sen. Vance Hartke of Indiana and actress Shirley MacLaine, who recently took her film "The Turning Point" to Havana for a special screening.

"This is the only party I would go to where cigars wouldn't make me sick," said MacLaine, who mentioned that Cuban President Fidel Castro had, following her visit, sent her a personal photo album of her trip as well as a "very long note."

For Laurence Birns, director of the Council of Hemispheric Affairs, a recently formed group that investigates human rights violations, the crowd ranged "from the approvers to the mildly critical. The very critical aren't here," he said. "I thought it was extraordinary that no one was searched at the door. It was very casual. The party was conducted as if once a week a bomb wasn't set off in some Cuban facility somewhere."

Another guest described the gathering as "the old left, like lawyer Leonard Boudin, the new left - The Institute of Policy Studies Group - and others like the State Department and businessmen types."

For Boudin, father of Kathy Boudin, a member of the Weathermen who went underground in 1970 and has yet to resurface, the evening was a mixture of business and pleasure.

"In July 1961 I singed an agreement with the Cuban government to represent them in all of their American legal transactions. To me this party signifies what I hope will be a change in my role from litigation to negotiation. But don't expect it to happen overnight."

As for the whereabouts of his daughter, Boudin would only said, "I love her and I admire her. But, of course, I can say nothing more."

Noticceably absent were Capitol Hill figures even though Sanchez-Parodi said they had been invited. He excused their absence by virtue of the recess and Hubert Humprey's funeral.