Gnathostorna doloresi, a nematode parasite producing ulcerative and/or granulomatous lesions in the gastric wall of domestic pigs and wild boars (Sus scrofa leucomystax) throughout southeastern Asia, is an important zoonosis causing cutaneous larva migrans in humans. Patients infected with G. doloresi have been found yearly in the vicinity of Miyazaki Prefecture, Japan. Adult nematodes were found in 31 of 32 wild boars captured at two different geographic locations in the prefecture, a location in the high mountains and one at sea level. The parasite-free animal had gastric ilesions typical of a previous infection with this parasite. The nematode intensities were higher in wild boars caught in the mountains than those caught at near sea level. The extremely high prevalence of G. doloresi in wild boars indicates that the life cycle of this parasite is well established in this area of Japan.