It's a long, long time between Chris Rock specials on HBO -- it's a long, long time between everything on HBO -- but that doesn't mean other performers on other channels aren't doing their best to pick up the slack and brighten the night with laughter. Dave Chappelle cranks it up to about 500,000 watts or so on "Dave Chappelle: For What It's Worth," the stand-up comic's new Showtime special, premiering at 9 tonight.

Like Rock, Chappelle is young, smart, irreverent and capable of provoking truly strenuous laughter. The special, taped in June at the historic Fillmore in San Francisco, gives Chappelle free rein, whatever that means exactly, and he scours the comedy surface of the Earth for subjects that range from predictable to out-of-nowhere, managing to make them all funny, if not equally so. This is one case where inequality is not necessarily a bad thing. Chappelle would rather be a little raggedy than too slick, and that attitude helps make the material seem fresh no matter how many times he might have done it. The laugh he gets out of one word taken from a current credit card commercial? "Priceless."

All of today's comics and would-be comics are virtually required to do a few Michael Jackson jokes or risk losing their comedy license, but Chappelle finds an approach to this major controversy of our time that is strictly his own. None of it can be quoted here, but if it could, why would you pay for Showtime? You could just read it in the newspaper. Of course the real reason it can't be quoted here is because most of the words are at least R-rated, which you doubtless surmised by now even if not familiar with Chappelle's work.

He enjoys that work, which is good, and now and then he convulses at some of his own comic ideas, suggesting that they may have originally come to him when he was in a state of slight intoxication. Or not, because one hardly needs to be stoned to find it funny when the gigantically lanky Chappelle recalls chasing a crackhead for blocks to retrieve a near-worthless candy bar swiped from his car, or to crack up when he announces that "from now on, I smoke weed only with white people" because "all they talk about is other times when they got high."

Chappelle is, in fact, making a study of white people, he says, with the first step an attempt to pin down the difference between "grape drink" and "grape juice." Chappelle talks about encounters with black celebrities, Native Americans and enterprising Asians (a Korean man incensed at being mistaken for Chinese) and, incredibly, gets some of his biggest laughs when he looks back on the alleged origins of the AIDS virus.

For many years, and maybe to this day, the birth of AIDS was blamed on, as Chappelle succinctly says, "People having sex with a monkey." He takes the simple statement, which for some reason everybody accepts without blinking, and follows it to its absurd and insane implications. The result is bitterly and meaningfully funny.

One Chappelle story, about a man creating havoc on a bus by wielding a weapon of sorts, goes on way too long; his tirade about the idiocies of Draconian anti-smoking laws isn't long enough; and an essay on the subject of "how old 15 really is" is probably just the right length, and makes just the right point. Near the very end, Chappelle allows himself a little sentimentality, talking about his family, and he does it with just the right, sweet touch. Only a comedian with true understanding and command of his audience can take such risks. Chappelle is in the top echelon of American comedy.

He ought to get credit, too, for taping his concert in San Francisco and yet restricting himself to only about a half-dozen gay references. Chappelle never takes the easy way, but he makes you laugh the hard way. Priceless.

Chappelle gets a

Showtime special.Chappelle's Showtime special, taped in June at the Fillmore in San Francisco, premieres at 9 tonight.