A case of intestinal anisakidosis in a 42-year-old man in Japan is presented. His chief complaint was an acute onset of severe abdominal pain. Approximately 12 hours before the onset of this symptom, he had eaten sliced raw mackerel ("sashimi"). Upper endoscopy was unremarkable. At exploratory laparotomy, an edematous, diffusely thickened segment of jejunum was observed, which was resected. The postoperative course was uneventful. The segment of small intestine showed a granular indurated area on the mucosal surface, and microscopically, a helminthic larva penetrating the intestinal wall, which was surrounded by a cuff of numerous neutrophils and eosinophils, as well as diffuse acute serositis. A cross section of the larva revealed the internal structures, pathognomonic of Anisakis simplex. Although anisakidosis is rare in the United States, with the increasing popularity of Japanese cuisine, the incidence is expected to increase, and pathologists should be familiar with this disease.