Jay Leno knows what America likes to laugh about. Burger King. Wonderbread. Grecian Formula TV commercials. Motels with noisy ice machines. The great common denominators that everyone can relate to and no one can take offense at.

It's what makes Leno America's favorite stand-up comedian (not counting Bill Cosby, who mostly does sitcoms and Jell-O commercials now). Of course Leno also does Doritios commercials, but what he's known for most is his routines - on Johnny Carson's Tonight Show and Late Night with David Letterman and in sometimes as many as 300 cities a year.Thursday night he stopped briefly in Salt Lake City and brought a full house to Symphony Hall. From the moment he walked on stage, and for two full-speed hours, Leno touched on the topics that Americans understand without having to think too hard about or be embarrassed by - cheese nachos, Star Trek, aging relatives who can't figure out what to say into your answering machine.

There was no warm-up act. He didn't need one. Leno just loped onto the stage - a little portlier and grayer than he looked when he was in Salt Lake City three years ago - and plunged right in with a timely cyanide-laced Sudafed joke:

"It's probably the same guy who's switching the regular coffee with the Folger's crystals," mused Leno, making a reference to something he could be pretty sure his audience would relate to - a TV commercial.

And then he added a bit of Leno absurdity: OK, so we go into the drug store and make sure the bottle of pills we buy has a seal around the lid and the whole thing is encased inside hermetically sealed plastic. And then we walk into the mall and a Hickory Farms lady comes up to us and says "Here, have one of these," and we eat it without a second-thought.

Leno, who spends a lot of his life as a frequent flier, told lots of airline jokes and some routines that fans will remember from other appearances (the thirtysomething jokes, the Three Stooges routine). But he also had some newer material. In drought-striken California he told the audience, robbers are breaking into people's houses these days "just to take a drink from the water bed."

Leno's observations are sometimes caustic. "Burger King's french toast is bread that's been re-breaded and dipped in oil," he noted, adding: "This is what people used to call a torch." But his observations are fueled more by wonder than anger or condescension.

Even his political jokes are gentle, and they, too, often include a reference to popular American culture: In Russia, he notes, people are waiting two hours in line at McDonald's - but not to buy hamburgers. "They don't even know what hamburgers are. They're waiting in line for the napkins."

And when he makes fun of his Mom and Dad, you can sense the love beneath the ribbing. He bought them a VCR for Christmas, he says, but they can't figure out how to use it. So basically what he bought them, he notes, is "a $1,200 digital clock." Although, of course, they can't figure out how to set that, either. But they do use the flashing 12:00 as a night light to find the bathroom.