The Department of Health, Education and Welfare continued its monthly Distinguished Speakers Series yesterday at noon in its North Building Auditorium on Independence Avenue. Previous speakers in the series - designed to "provide insights and intellectual stimulation for HEW employees" - were President Mondale, who talked on the American family, and United Nations Ambassador Andrew Young, who lectured on America's role in the U.N. and in world affairs. But yesterday the series planners had something different in mind: Art Buchwald.

Right off, HEW Secretary Joseph Califano - who had his right arm in a sling, the result of a recent operation on his thumb - set the tone. "This is a man I've driven to Redskins games for 10 years," Califano said, adding that Buchwald has yet to fork over 10 cents for gas. The secretary then said Buchwald's life mocks everything HEW stands for. Not only is he a high schoola dn college dropout, but his idea of physical exercise ends at hailing a cab, or maybe turning on his electric typewriter. And as for smoking, well, "there are some who claim he came out of the womb with a cigar."

Then it was Buchwald's turn. The 52-year-old syndicated columnist came on sounding like a tuba with a Queens accent. "Only in America could someone like Joe Califano become Secretary of HEW, and Larry Flynt, the publisher of Hustler, become a born-again Christian," he said. (He does this sort of thing all the time, usually for a couple thousand dollars a shot; yesterday it was a gratis appearance.) Next he spoke of Califano's low profile. "He has never appeared on TV between 1 and 5 o'clock in the morning."

He dished it out to the secretary awhile longer, mostly cracks about hiring a personal chef and trips to see the Pope, finishing off with a line about Califano's folks. "You know, it's not widely known," Buchwald said, looking very sober, "but the secretary's parent are on Social Security. 'How could you do that, Joe?' I asked him. 'Well, I'd help them out,' he told me, 'but I believe in character building.'"

After that Buchwald turned his fire on other targets. "I worship the very quicksand Jimmy Carter walks on," he said. He then focused on Carter's Playboy interview. He said there's a new bumper sticker out: IN HIS HEART, HE KNOWS YOUR WIFE. Of Jerry Ford: "I believe he'd still be in the White House if he hadn't freed the Polish people prematurely." Of gun legislation and the National Rifle Assn., a favorite Buchwald target: With me, it's very personal - my neightbor has a gun and he can't even water his lawn straight."

At the end of the hour, Buchwald was presented with a plague, honoring him as "the premiere American humorist" of our time. Califano had earlier called him a spiritual descendant of Ambrose Bierce, Mark Twain, Will Rogers. Buchwald had no comment on that.

Buchwald's talk was simultaneously translated into sign language by a young woman named Virginia Lewis, who stood beside the humorist onstage as he spoke. Lewis is an employee of HEW and has worked with him before, at a talk at Gallaudet College. "I kinda liked the routine," Buchwald said to her in the hallway afterward. "Why don't we team up?" Then he lit up a cigar and took autographs.