"The Exterminator" opens with an explosive flourish, as a silhouetted rifleman is blasted into the night sky. Burst of napalm provide infernal illumination for a setting revealed to be Vietnam and a prologue cribbed from the famous atrocity and escape sequences of "The Deer Hunter."

Touching many a familiar base in its violent, blatant scamper for the exploitation dollar, "The Exterminator" moves from Vietnam to Hoboken (I think) while depicting the emergence of an ex-Gi as the greatest scourge of urban criminals since Charles Bronson in "Death Wish."

In the prologue, three American soldiers are captured and placed at the mercy of a Viet Cong interrogator. One is promptly beheeaded. Somehow, one of the remaining prisoners contrives to disarm prisoners contrives to disarm his guard, blast the captors and free his buddy.

The scene shifts to aerial panoramas of the New York skyline at might. This portentous overview seems to terminate on the Jersey side, where the surviving soldiers, John and Michael, now reside in the same apartment building and work at the same warehouse.

John, played by Robert Ginty, is white and unmarried; Michael, played by Steve James, is black and a happily married family man. Back in Nam it was Michael's elusive heroics that saved their lives. History repeats itself at the warehouse: John surprises a trio of neighborhood burglars, and Michael arrives they're holding his buddy at knifepoint.

The next day Micheal is set upon by an augmented gang of toughs and beaten into a state of permanent paralysis. This brutality provides the justification for John to emerge from his ineffectual cocoon as a grief-stricken but quietly efficient killing machine.

After shooting one of the assailants and arranging for two others to be nibbled by famished rats in a garbagestrewn basement, John Kidnaps a local mobster and holds him for ransom to raise the money for Micheal's hospital bills. When the mobster attempts a double-cross, John deposits him in a huge meat-grinder.

Branching out, John exacts bloody vengeance on a couple of whoremongers who have branded a young hooker and then a group of muggers who have assaulted an old lady. He declares his determinator." Soon he has a personable cop, played by Christopher George, on his tail -- as well as a CIA hit man acting on behalf of the presdient, who is insulted that anyone should cast doubt on his ability to defend law and order in an election year.

"The Exterminator" is socially undersirable stuff -- a lurid, vicious exercise in urban paranoid fantasy and aggressive wish-fulfillment. Writer-director James Glickenhaus takes obscene relish in the atrocities and the reprisals. The episode about the victimized prostitute is inserted out of the porno-violent blue, and highlighted by lingering over shots of the bare-bosomed girl shrieking in terror while a torturer dips a blazing soldering iron into a jar of Vaseline.

At the same time, the sensationalism owes part of its impact to the fact that James Glickenhaus, whoever he is, displays a considerable flair for stimulating effects. The hellish nocturnal imagery imposed in the early sequences is sustained with vivid consistency, recalling the mood of "Taxi Driver" and "The Warriors."

Glickenhaus has enough skill to generate intense kinetic excitement out of trumped-up pretexts. For example, the mugging episode is miserably contrived, yet it culminates in a showdown between the avenger and an onrushing car that is cut with teeth-gnashing effectiveness. In addition, Glickenhaus seems to have a knack for wacky little character details -- detective George uses two forks attached to his desk lamp to heat a hot dog for lunch -- and audacious shifts of mood. He can enhance a basically grim situation by interjecting something incongruously funny. The most astonishing example depicts the afermath of a death scene in a hospital room: At the sound of an alarm, an empty corridor is suddenly filled with doctors and nures jolted out of erotic hideaways.