Enterobius vermicularis (pinworm) infestation is quite common, especially in children and their caregivers. Often infection is symptomless, but more often there is perianal itching due to the adult females, which lay the eggs in the perianal region. Reinfection and person-to-person transmission is common. During colonoscopy, the adult female worms can be seen in the cecum, ascending colon, or distal ileum as white worms of 8-13 mm in length. This article is part of an expert video encyclopedia.