HOSTEL — ** 1/2 — Jay Hernandez, Derek Richardson; rated R (violence, gore, torture, profanity, sex, nudity, drugs).

Eli Roth won't just show you a close-up of a chain saw severing the fingers of a hapless backpacker who's been chained to a chair and tortured. He'll also show you the bloody stumps falling onto the dark stone floor, as well as the partial paw that remains.

Such is the relentlessly graphic nature of "Hostel," which surely must have been intended as a homophone for "hostile," and is not for the faint of heart. (Reportedly not one but two ambulances were called to care for audience members who fell ill while watching the horror movie during last year's Toronto Film Festival. Coincidence? Perhaps not.)

Roth follows up 2003's "Cabin Fever," the writer-director's darkly funny gross-out debut, with the story of Ugly Americans and their Icelandic pal who are traveling across Europe seeking thrills, but become the victims of someone else's twisted idea of fun.

And "Hostel" is extremely effective in achieving its goal: to make you squirm in your seat, heart pounding, fingers splayed across your eyes, in sheer amazement at the intensity of the images on the screen. A lot of horror movies come out every year but few of them are truly disturbing. This one is.

Roth builds tension slowly and takes his time in torturing us — and continues to reveal himself as a filmmaker of control and confidence beyond his 33 years. (Quentin Tarantino apparently agrees, serving as an executive producer and providing the "Quentin Tarantino presents" tag above the title.)

Nothing violent occurs for the first half of the film, as twentysomething friends Paxton (Jay Hernandez from "crazy/beautiful") and Josh (Derek Richardson from "Dumb and Dumberer") smoke hash and chase foreign women with their new pal, Oli (Eythor Gudjonsson), who likes to call himself "the king of the swing." Bars, brothels, they don't care where they have to go for the best time money can buy. And you'd swear you'd wandered into a bawdy, buddy sex comedy.

Then a stranger encourages them to take the train to Slovakia, where there's a hostel with the most amazing women who will do everything imaginable. Young, stoned and far from home, they say why not — and the women they meet there don't disappoint.

Their exotic roommates, Natalya (Barbara Nedeljakova) and Svetlana (Jana Kaderabkova), have a propensity for walking around topless by day and drinking and dancing by night. Everything falls into Paxton and Josh's laps too easily — including Natalya and Svetlana — until they each find themselves handcuffed to chairs in a dungeon room with a variety of sharp tools and wild-eyed people with ideas about how to use them.

Yes, "Hostel" is dizzying in the violent acts it depicts, but it's also surprising in its ability to garner sympathy for its characters, who seemed so obnoxious in the beginning. (Though, to be fair, Josh is the more decent of the two. You can tell because he uses an asthma inhaler.)

But the main point, without giving too much away, is the idea of torture as sport — arbitrary, elaborate, depraved. And whether or not this kind of horror movie is your cup of tea, you have to at least admire Roth for the daring and creativity with which he illustrates that concept.

"Hostel" is rated R for brutal scenes of torture and violence, gore, profanity, sex, nudity, drugs. Running time: 95 minutes.