Primarily a showcase for the gory special-effects artistry of Gianetto de Rossi, this revolting horror film stars Giovanni Lombardo Radice (also known as John Morghen) as a drug-dealer who comes to the Amazon jungle from New York looking for a cache of stolen emeralds.
He joins some American college students and soon introduces them to his special lifestyle, raping a native girl, then beating a young Indio senseless before gouging out his eyeball with a knife.
Naturally, the local cannibals don't take too well to this treatment, so they cut off Radice's penis with a machete, gouge out his eye, then scalp him and eat his brain. Deciding that his companions are also to blame, the natives hang a young woman by impaling her breasts on meat hooks while her sorrowful companion sings Red River Valley.
Eventually, one woman gets back to New York, where she reads a dissertation on cannibalism to earn her PhD. Cult filmmaker Umberto Lenzi really outdid himself with this bloody spectacle, which maintains a consistent air of cruelty with a non-stop procession of beatings, rapes, real-life animal slaughter, larva-chewing, genital-chopping, cannibalism and the infamous meathook scene.
Definitely for acquired tastes only, this nauseatingly effective shocker features a brief appearance by adult-film star Richard Bolla as a New York policeman.