A four years old boy presents with suspect acute appendicitis and surgical removal was decided. The surgical diagnosis was acute appendicitis but the pathological diagnosis was Enterobius vermicularis infection in removed appendix. Appendicitis is rare in children < 5 years of age and is more difficult to diagnose in young children. The role of Enterobius vermicularis as a cause of acute appendicitis remains controversial. Enterobius infestation may be associated with acute appendicitis, chronic appendicitis, ruptured appendicitis, or without clinical symptoms 1. To the best of our knowledge, there are no studies of incidence of acute appendicitis due to Enterobius infection nor case report in Taiwan.