A fistula-in-ano is a communication between the anal canal and the perineal skin. Most cases of fistula-in-ano occur in adults. Fistula-in-ano in infants occurs exclusively in males. Generally, fistulae-in-ano are considered a consequence of an underlying perianal infection. This chapter discuss the etiology, classification and treatment of perianal abscess and fistula-in-ano in children.