Andy Warhol, the artist, set off the metal detectors with his camera and battery pack. But he didn't mind the security check. "It's okay with me," he shrugged.

"It's just one of those things you do when you're a groupie for Ron."

He was referring to Ronald Reagan Jr., the president's son and a performer with the Joffrey II Dancers, which made its Washington premiere last night at George Washington University's Lisner Auditorium. Metal detectors and handbag checks were just part of the strict new security procedures used because the president and Nancy Reagan were in attendance. The White House had requested 300 tickets for the event and so the presidential party was a sizable portion of the audience. It included Ron Jr.'s wife, Doria.

Security was so tight that the presidential motorcade from the White House to the Lisner, about a mile away, contained two nearly identical black limousines -- one apparently a decoy. The president and Mrs. Reagan rode in the other.

Despite, or perhaps because of, the strict security, the performance went off without a hitch. Afterwards, Ron introduced the company's dancers to his parents. Nancy Reagan, hugging Ron, said, "I never knew you could do that."

The president said the performance was "just wonderful," and added, "this is only my second trip to George Washington University [a reference to his recent stay at the university's hospital] and I enjoyed this one so much better."

The president said his particular favorite was the company's last number, "Threads from a String of Swing," performed to Glenn Miller music. "That was so nostalgic," he said. One of the dancers called out, "We did that just for you."

The swing-inspired number was also a favorite with many of the guests at a post-performance reception at the embassy of New Zealand.

"That Glenn Miller number was just grand," said presidential counselor Edwin Meese."I have known Ron since he was a little boy, and I thought he did an outstanding job tonight."

"It was just wonderful," added Charles Wick, director of the International Communication Agency. "Quite enjoyable, even for a non-balletomane."

None of the Reagans attended the party, but Ron Jr.'s performance was still the talk of the evening.

"He [Ron Jr.] seems so sweet and unspoiled," said Washington socialite Ina Ginsburg. "We all felt for him . . . it's not an easy thing when the whole town comes to watch you."

"I thought Ron was tremendous," said Carolyn Deaver, wife of White House deputy chief of staff Michael Deaver, "considering the fact he's only studied about five years."

"Young Ron really was quite good," said Attorney General William French Smith. "I'm not much of a ballet critic, but I thought it was well done."

We were all holding our breath," said Casey McCoy, wife of Peter McCoy, Nancy Reagan's chief of staff. "Everyone who had anything to do with the family was very anxious for him. I was very impressed."

The night's other conversation piece was the new security procedures. "It's sad that it has to be done," said Peter McCoy. "But after the pope and Reagan's being shot, it just has to be done,"