A 50-year old man developed epigastralgia one day after eating a raw squid meal. A submicosal tumor-like gastric lesion at the gastric fornix was demonstrated on gastroscopic examination. Manifestations of acute gastritis were also seen. In 5 days (the period between the first and the second examinations), the tumor disappeared and a large ulcer was seen endoscopically at the same site. Biopsy epecimens revealed eosinophilic infiltrations at the site of the lesion. Mild leukocytosis, significant eosinophilia and high serum anti-Anisakisantibodies were also revealed. The patient was closely followed-up by endoscopy, endosonography, barium studies and laboratory investigations until the ulcer was completely healed. The lesion was probably caused by gastric anisakiasis and could be categorized as a so-called “vanishing tumor of the stomach”.