Polyarteritis nodosa (PAN) is a systemic necrotizing vasculitis, which affects predominantly medium size arteries. It has been described in humans, occurring more often in young adults. Small arteries may also be involved, but there is no involvement of smaller vessels, including arterioles, capillaries, and venules. 1 In animals, PAN has been reported in sheep, 2 dogs, 3 cats, 4 pigs, 5 and rats. 6 Among non-human primates, the disease has been described in cynomolgus monkey (Macaca fasciculares), 7,8 rhesus monkey (Macaca mulatta), 9 and owl monkey (Aotus sp.). 10 The common wooly monkey (Lagothrix lagotricha) is a New World primate with a wide distribution range in the Amazon Forest 11 and listed as vulnerable, with a decreasing population trend. 12 Here we describe a case of