Punk rock reunion tours are an iffy proposition. Mess it up and the legacy goes out the window.

The good news is, X is safe.

The venerable LA band returned to Pittsburgh for the first time in 20 years Friday at the Rex and it was as good or better than the last time.

Of course, it's hard to go wrong when your guitarist is a replicant from "Blade Runner." That's the only way to explain Billy Zoom. The statuesque guitarist with the blond pompadour spends the whole show with a grin that says "wheee, look at me!" while he rips off killer runs with uncanny perfection. Even in his biker jacket, he barely breaks a sweat.

Meanwhile, on the other side of the stage, is the anti-Zoom -- singer- bassist John Doe, with sweaty hair flying in his face, seeming like he's playing for his life up there. His dual role is to help drive the rhythm section with the irrepressible D.J. Bonebrake and find some ragged harmony with former wife Exene Cervenka.

Exene was never the typical frontwoman and now she's even less so. She hit the stage looking like a hausfrau with her scraggly hair, polka dot granny dress and athletic tube socks. Vocally, she's thrust into the position of the damsel getting overwhelmed by the train.

The whole thing didn't gel right away. The first few songs - "The Phone's Off the Hook, But You're Not" and "White Girl," among them - felt static and the vocals were a murky mess. Then, right around the signature song, "Los Angeles," Doe broke a sweat and it was like the electricity flipped on. X started slamming one 3-minute song into the next with punk-rock abandon. Twenty years ago, the same fans below would have been throwing their bodies at each other, adding to the furious energy. But, hey, they have real jobs now, so last night, it was reserved to mere bouncing and devil horns in the air.

X played everything we wanted to hear from the first four records, tearing through the seedy thrash of "Johnny Hit and Run Paulene" and "Motel Room in My Bed"; the off-the-rails abandon of "We're Desperate" and "True Love"; the metallic sludge of "Nausea" and "The Unheard Music"; the retro punkabilly of "Breathless"; the cascading clatter of "Hungry Wolf" and the "New World," with its still-timely chorus of "it was better before, before they voted for what's-his-name."

After it seemed as though X and its fans had exhausted all the energy supply, the band returned with a final thought: "The World's a Mess, It's in My Kiss."

Could it be that back in the day X made a deal with the devil? How else to explain such punk-rock fury past the age of 50.