The International Herald Tribune published a slide show documenting the Tinku ritual in Bolivia. Here is how they describe it:
For hundreds of years, the Indians of Bolivia’s high plains have trekked to the town of Sacaca in early February. They dance, drink chicha, the fermented beverage made here from rye, and then fight one another until blood stains the dirt alleyways.
Tinku is the original ultimate fighting tournament. It’s not uncommon for the fights to end with one of the participants dying. More photographs can be found at photo-mundo.com . There is also an article in the New York Times (registration required) explaining the ritual.