Although perianal ulceration is common in Crohn's disease, extensive perineal ulceration particularly in children is rare. The case history is presented of a child who developed progressive hypertrophy of the vulva and ulceration of the groins at the age of 11 years but diagnosis of Crohn' s disease was delayed for 21 months. Treatment with steroids and azathioprine has induced a successful remission but difficulty has been experienced in reducing the steroid dosage.