Crucifixion. Cannibalism. Slow death by eating glass. Sexual mutilation. Is there nothing Tom Fontana won't depict on his HBO prison series, ''Oz''?

''The problem with TV violence, it's a lie,'' said Mr. Fontana, who writes most of the show's episodes and is one of its executive producers, along with Barry Levinson and Jim Finnerty. ''People get shot and don't bleed. They get hit and walk away. If you have to do it, you have to do it as horrifically as it really is.'' And Mr. Fontana is really trying as hard as he can.

At its worst ''Oz,'' which begins its third season on Wednesday looks as if it had been conjured up by adolescent boys trying to gross each other out. At its best, though, ''Oz'' has elements of Greek drama (including eyes being gouged out). There is also a chorus, in the person of a crippled convict, Augustus, played by Harold Perrineau, who narrates episodes from a glass cage. He even quotes de Tocqueville.

So far ''Oz,'' one of HBO's highest-rated dramatic shows, has received mostly favorable reaction. The critic Stanley Crouch, writing in The New York Times Magazine, praised it for its ''consistently brilliant acting -- some of the best in the history of television.'' The show, Mr. Crouch wrote, ''is a landmark for the medium.''