More than 800 people last night pulled out tuxedos and minks for one of Washington's biggest bashes ushering in the 1984-85 social season.

The sixth annual Multiple Sclerosis Ambassadors Ball included the traditional receiving line and dancing after dinner. Edwin and Ursula Meese and Steve and Joyce Bell headed up the greetings. The presidential adviser was in top form, balancing a drink on a chair behind him, his wife beside him, the press all over him and a relentlessly long line of well-wishing guests in front of him.

"This is a famous event in Washington," said Meese about the benefit, which is expected to raise at least $175,000 this year. "This is the only event that guarantees to get Steve Bell here," Meese added, grinning at the newscaster from ABC's "Good Morning America."

"Right!" Bell kidded back, interrupted by another handshake.

"Are we on full-time duty all night?" Meese wearily asked Bell after 15 minutes of constant shake and smile. "When does our relief appear?"

But Meese continued shaking hands, sporadically interrupted by friends and acquaintances who would sotto voce make reference to the not-yet-released report dealing with Meese's finances, which came under criticism during his nomination hearings to be attorney general. "When does the report come out? They better hurry up," one guest told Meese.

"It was obviously the right decision," Meese answered when asked to comment on the decision made by Senate Judiciary Committee Chairman Strom Thurmond (R-S.C.) to remove Meese's nomination from the calendar.

The man Meese was nominated to replace, Attorney General William French Smith, answered the same question just as quickly. "That's an easy question because I cannot comment on that . . . we'll leave it up to the discretion of the Senate Judiciary Committee."

When the topic turned to dancing, the attorney general's wife, Jean, chimed in, "He's a superb dancer." Surprised, Smith said, "I am? How nice of you to say that."

Agriculture Secretary John Block and his wife Sue also showed up to show their support for the battle against MS. The couple had donated to the evening's silent auction a dinner for six at their home.

Block was in a particularly chipper mood, as he had had an "excellent day. The president offered 10 million metric tons of additional grain to the Soviet Union. We have a good crop and we need to sell it. So it's a good day for agriculture and a good day for the secretary of agriculture."

Selwa Roosevelt, chief of protocol, toasted the ambassadors at the ball and reminded everyone of the purpose of the evening. "This gala evening, as you know, benefits the National Multiple Sclerosis Society. MS is an international problem knowing no political boundaries . . . thus, we especially salute tonight the spirit of international cooperation in seeking to eradicate, through research and research dollars, MS, the most prevalent neurological disease affecting young adults."