Petwo (also written Petro) is the second of the two principal rites of Haitian Vodou, paired with and contrasted to Rada. Where Rada is described as cool and rooted in the ancestral traditions of West Africa, Petwo is described as hot, fast, forceful, demanding and effective, and is generally understood to have taken its distinctive shape in the Americas, drawing together Kongo and other Central African elements with West African and, some argue, indigenous Caribbean ones.
Its rhythms, drums, songs, colours and offerings differ from Rada's, and the two are kept ritually apart. The rite is associated with fire, with gunpowder, with the crack of a whip in some services, and with a directness of exchange between practitioner and lwa in which results are expected promptly. Ezili Dantor, Met Kalfou, the Simbi and the Bosou are among the lwa most associated with it, and many spirits have both Rada and Petwo aspects, so that the difference is one of manner and approach rather than of roster.
Scholars and practitioners regularly note that Petwo's character is bound up with the history of slavery and revolution in Saint-Domingue. The rite's force and urgency are frequently described as a religious formation shaped under conditions of extreme violence, and the ceremony at Bois Caiman in August 1791, traditionally associated with the outbreak of the Haitian Revolution, is remembered within the tradition as a Petwo service. Historians debate the details, and in some cases the historicity, of particular elements of that account while generally accepting the broader connection between Vodou and revolutionary mobilisation.
The most persistent outside misreading is that Petwo is the "black magic" half of Vodou. Ethnographers of the religion reject this consistently: the distinction is between cool and hot, patient and quick, not between good and evil, and the moral evaluation of an act in Vodou turns on what is done and why rather than on which rite is used. The association of Vodou generally with malevolence in Western popular culture has a documented history in the literature and film of the United States occupation period, and it has had real consequences for Haitians, including within Haiti, where Vodou was subject to periodic Catholic and state campaigns of suppression, most severely in the "anti-superstition" campaign of 1941-42, before being granted official recognition as a religion in 2003.