A Biohazard seethes in Brooklyn.

It's a frigid black night in a deserted parking lot in Williamsburg. I'm pretty sure I'm in the right place when I see the tricked-out black Suburban with garish chrome accents and flames down its sides. Flanking it are a sensible cherry-red Daewoo and a Volvo hatchback with antiwar stickers on its bumper. The Suburban must belong to Evan Seinfeld, bassist and front man of the hardcore band Biohazard and a bit actor in seasons two through five of HBO's Oz.

Good guess. As Seinfeld would tell me later that night, "I drive up and down these streets in my fuckin' flame hotrod truck, ruling these streets around here. That's why I feel really weird in this gentrified Brooklyn? Where I grew up was full of tough guys, and I live in this weird neighborhood where everybody's, like, nerdy art people. I'm the only guy in my building from Brooklyn. Go out in the parking lot, and all the plates are like North Dakota, Ohio, Connecticut."

The rock star buzzes me into his converted loft building, where we talk until two in the morning.

At 18, says Seinfeld, it struck him that he'd attended something like a hundred funerals but not a single wedding. He'd grown accustomed to seeing his friends in Canarsie die by murder, suicide, overdose, car accident. He describes his old hood as Goodfellas territory: "Every wise guy in the world either lived in Canarsie or was traipsing through? So there was this crazy Bronx Tale feel to it? I don't even remember crying after I was about 12 years old. For me the outlets were the streets and drugs, alcohol and music."

Then, Canarsie was Italian and Jewish, and was bordered by the New York Harbor on one side and by black and Hispanic projects on its other two.

Music was Seinfeld's out. He grew up on Sabbath, Maiden and Priest, but by the time everyone else discovered those groups, he'd moved on to Slayer and Motorhead. Then came hardcore?the Cro-Mags, Bad Brains, Suicidal Tendencies, Minor Threat. Seinfeld picked up the bass when he was 13. A week later he played his first gig in a band that covered the Ramones, AC/DC, Van Halen and the Who.

"I think music is born into you," he says. "It's bred into you like fighting is bred into a pit bull."

Seinfeld, 31, is muscular, just shy of six-feet, paunchy. He's a straightforward guy, nice but abrasive. The pencil-drawn goatee and shaved head of his Oz character, Jaz Hoyt, are now wispily overgrown and shaggy. Tattoos cover some 60 percent of his body, he says.

His fiancee, porn star Tera Patrick (on her way out of the business), isn't around, but as we talk, a miniature fox terrier and an orange tabby cat wrestle behind me while Sammy, Seinfeld's eight-year-old boy from his ex-wife, runs around.

The bookshelf is populated by Nietzsche, Garcia-Marquez, meditation books and several basses and six-strings?including an original 70s Les Paul?lean against a wall; a glass display case is filled with gothy figurines. He built the second story in this enormous 24-foot-high space, complete with two bedrooms, but Tera's touches are evident: Arabian pillows and mattresses, ornate lamps, silk tapestries. It's opium-den chic, loungy Williamsburg; a thread of incense hangs in the chill air.

The first Biohazard lineup, circa 1987, was a quartet of Canarsie blue-collar kids who liked to have their fun.

"It was purely accidental. We were all fucked up. I was fucked up on coke, one guitar player was a drunk and the other guy was doing heroin. We were just a bunch of fucking junkies, basically."

Seinfeld says he was dealing coke at the beginning and that that's how he paid for the band's first rehearsal space. At one point he went upstate for a year to go to college and then dropped out, and when he came back was when crack hit.

"We were smoking crack before it was in the news. It wasn't like 'CRACK KILLS.' There was no slogan yet. So we were all hooked on crack and we didn't even know it."

Though Biohazard pioneered the melding of metal and hiphop, the band hasn't seen the megabucks awarded to other artists since the rap-metal explosion of the late 90s. Seinfeld says it doesn't make him bitter; he's satisfied with his fans' intense loyalty, pointing out that thousands have emailed him photos of their Biohazard tattoos. Still, he's not uncritical of the bands that did snag those megabucks.

"Groups like Limp Bizkit came out and did a little of our style, added a DJ, and then made like really cheesy hooks about 'I did it all for the nookie' or whatever, and America runs out and buys it because they're force-fed? I talked to Fred [Durst]. I was like, what does Limp Bizkit mean? He goes, 'It means nothing, that's the whole point, it's like Seinfeld, it's about nothing.' That's the gag, and everybody buys it, ha ha ha. And they're laughing all the way to the bank, and good for them."

Seinfeld likes Korn and the Red Hot Chili Peppers, and liked Rage Against the Machine's first album, but thinks Rage should have shelved the politics: "They're singing about how they want to turn America Communist and raging against the machine, as they say, but here they are signed to Sony, the biggest multinational corporation ever, and they're part of the machine, like it or not? They should have just been a fun rock band. Or they should have went all the way with it and made their own record label and distributed it themselves and shared the money communally. That would have been hardcore."

The Oz gig and the constant touring have afforded Seinfeld a comfy lifestyle. He gets off on his own cynicism as an original Brooklyn boy in gentrified Williamsburg, and likes to joke about what he sees around him. He says that when he was coming up, the neighborhood was Hasidic and Puerto Rican. Now, he says, it's about mom-and-pop shops, only "there are no mom-and-pop shops; they're trust-fund kids who opened a store with their parents' money, mostly."

The gentrification transplants, he says, dress "designer homeless? They're wearing Jil Sander Pumas, like $500? It's not a friendly atmosphere. There's a lot of really angry like lesbian chicks around. I don't care what anyone's gender preference is, I like to live and let live, until you look down your fucking nose at me? Everyone here is very nonconfrontational, very stop-the-war? The coffeeshop where everyone goes, they're giving out these don't-bomb-Iraq stickers. I'm looking to get a whole bunch of them and cut out the 'don't' and put them on my Suburban and drive around the neighborhood.

"I think everyone is scared of me around here because they see my biker friends coming over, everyone is wearing leather. We'll start up 20 bikes in front of the building. And most of these kids are driving like antique bicycles, trying to look?you know what it is, this whole hip-to-be-square thing. There's at least three guys in this building who wear glasses with a Band-Aid in the middle."

A couple weeks after our interview, Seinfeld hit the road in support of Biohazard's seventh album, Kill or Be Killed. He's working on a hiphop side project called Triple Sicks, and just read for a part in a Vin Diesel movie. He'd like to start an ultra-exclusive, custom-car shop strictly for "player" clients, in the spirit of L.A.'s West Coast Choppers. On top of all this?and managing his fiancee's career?he still finds time to coach his son's soccer team on the weekend.

He may not be a Fred Durst or a Zack de la Rocha, but he's all sincerity when he leans forward from his leather recliner and tells me, simply: "I live in a state of contentment I've never known before."

Biohazard plays Sat., April 12, at L'Amour, 1545 63rd St. (betw. 15th & 16th Aves.), Brooklyn, 718-837-9506, 7, $7.