Rave reviews for the Brazilian movie "Pixote," which opens today at the Inner Circle, suggest a powerhouse social drama -- a harrowing chronicle of juvenile delinquency in the slums of Sao Paolo and Rio, updating the tradition of classics like "Shoeshine," "Los Olvidados" and "The 400 Blows." While an undeniable shocker and upsetter, steeped in more than enough depravity to curdle the digestion, "Pixote" is also compromised by conspicuous structural defects.

The aims and skills of director Hector Babenco are sufficiently dubious to obstruct the emergence of a story or even an outlook that adds up emotionally, let alone in terms one might compare to the profoundly moving pathos of "Shoeshine" or the scathing clinical objectivity of "Los Olvidados." Evidently improvising from both a novel ("Infancia dos Mortos" by Jose Louzeiro) and the testimony of delinquent kids, Babenco ends up with a blurred, derelict scenario that rambles from vicious episode to episode without sustaining a sharp dramatic focus. At the same time, one detects an exhibitionistic tendency to wallow in vice for its own slummily picturesque sake.

The diffusion seems especially wayward because the initial approach to the audience is personal and straightforward. The filmmaker himself appears in a brief documentary prologue. He outlines the factual background that inspired the fictional narrative to come, emphasizing two points -- there are more than 3 million homeless children in the country and the penal code prevents anyone under the age of 18 from being prosecuted for criminal acts. The boy cast as the title character -- "Pixote," pronounced pee-shoat, a Portuguese slang expression identical to "Peewee" -- is introduced in a Sao Paolo shantytown, where the director found him residing with his mother and several siblings.

Theoretically, the story remains an account of the criminal miseducation of Pixote, a 10-year-old orphan so hardened by experience that he can become a remorselessly detached little triggerman. But in practice, Babenco can't keep Pixote at the center of things. Perhaps his young lead, Fernando Ramos da Silva, proved a less expressive non-pro than anticipated, or maybe Babenco lacked the experience or genius necessary to coax a psychologically complex performance out of him.

Plucked off the streets in a routine roundup of youthful flotsam, Pixote becomes an inmate at a teeming juvenile detention center. He finds a niche of sorts, attaching himself to an older group of boys dominated by two figures -- Jorge Juliao as an overtly homosexual teenager called Lilica and Gilberto Moura as a personable young tough called Dito.

There is a bewildering tangle of sequences in which the police, investigating the murder of a judge, lock up several boys and beat one, Lilica's lover Fumaca, to a fatal pulp. This provokes an ill-conceived reprise of Frank Sinatra's death scene in "From Here to Eternity," augmented by a fit of hysterics from the distraught Lilica. This is followed by a breakout. The action moves to the streets, where Pixote joins his peers in a series of criminal endeavors, progressing from purse-snatching in Sao Paolo to drug-dealing, pimping, armed robbery and eventually homicide in Rio.

Soon after arriving in Rio, the boys latch onto a peculiarly unappetizing mealticket, a hardbitten, rapacious hooker named Sueli, impersonated with hideous zest by Marilia Pera. They begin sticking up the clients she picks up. They also move in with her, Pixote looking on from the sidelines (or the foot of the bed, to be precise) as Dito asserts himself by discarding the adoring Lilica for the devouring Sueli. An unwholesome prospect to begin with, this grotesque family group fails to survive, and we're left with the image of Pixote on his own, a savage innocent wandering toward an unknown but presumably horrible future.

I could be missing some crucial cultural links that might be self-evident to Brazilians, but Babenco's thoughts appear to diverge rather weirdly during the transition from harsh institutional life in Sao Paolo to sleazy underworld domesticity with Sueli in Rio.

In all likelihood, Babenco lost the thread of his original argument and got carried away flaunting Sueli, who is certainly an unforgettable degenerate. She acquires more predatory force than any other element, human or sociological, in the picture. One might entertain the idea of victimization by such a lowlife femme fatale. But that seems to be another story and another problem.