We report a case of acute abdomen caused by the invasion of the ascending colon by larvae of Anisakis simplex in a 57 year-old-woman whose initial symptoms were colic abdominal pain, diarrhea and fever. The diagnosis was done by the histological study of the surgical specimen in which two parasites were morphologically identified in the submucosa. Although a causal relationship of the disease with the ingestion of crude fish could not be established initially, there were antecedents of ingestion of anchovy in vinegar (Engraulis encrasicholus) and dyspeptic symptoms for several months.