Leonardo DiCaprio delivers a knockout, Oscar-caliber performance in "The Basketball Diaries," the true story of high school basketball star Jim Carroll, who nearly destroyed himself with heroin.

But instead of trying to deal with this subject in some insightful way, the movie settles for exploiting and wallowing in the degradation of the central character's downward spiral — so much so that it often seems more like an endurance test than a piece of entertainment.

Based on Carroll's autobiographical journals and vaguely updated to a contemporary time-frame, the film begins as he is a basketball star in his Catholic high school in New York. Admired by schoolmates and loved by his divorced mother (Lorraine Bracco), Jim would seem to be on top of the world. But there's a dark side. His gay coach (Bruno Kirby) lusts after him, horsing around in school gets him regular beatings and in his off hours, as he hangs out with three rowdy friends, Jim begins a life of petty crime and experiments with drugs, starting with glue-sniffing.

It doesn't take long for things to get rougher, as Jim and his friends find their life of crime escalating into violent confrontations. And as drugs and sex lead him to discover euphoric escapism, his downfall is rapid.

As Jim begins missing school, stealing cash from his mother and gets into screaming sessions with her, she reluctantly kicks him out.

In a scene that demonstrates the film's heavy-handedness, Jim and his buddies taunt each other to dive off a cliff into the Hudson River, which is loaded with sewage. The metaphor is obvious.

The film's most touching moment comes later, when Jim, strung-out and hurting, returns home and his mother refuses to let him in. On opposite sides of the door, they both cry as he at first pleads, then begs, then angrily demands that she let him in. Knowing the probable consequences, however, she refuses.

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And in the end, there is a try for an uplifting moment of redemption — but it comes too quickly. And since there is no time spent on Jim's recovery, it has a hollow ring.

Too bad, since "The Basketball Diaries" has great power in certain individual moments and boasts some fine performances — Bracco, Ernie Hudson, Mark Wahlberg, Juliette Lewis) and especially DiCaprio (despite a physique that doesn't ring true for a basketball star).

But overall it's little more than just another downbeat, descent-to-hell druggie picture. We've seen it all before.

"The Basketball Diaries" is rated R for violence, profanity, vulgarity, nudity, sex, drugs.