Fistulas-in-ano may be classified as simple or complex, or according to their anatomy--intersphincteric, transsphincteric suprasphincteric or extrasphincteric. Most of them are treated surgically. Simple fistulas may be treated by fistulotomy, but complex or high fistulas require careful evaluation and often require alternative surgical procedures. In all instances, the objective should be to eradicate the fistula without compromising continence. Perianal disease may be present in 10% to 80% of patients with Crohn's disease. In these patients treatment must be individualized. Important considerations are the presence or absence of rectal disease, the complexity of the fistula and the strength of the anal sphincter muscle. Treatment options include fistulotomy, simple drainage or unroofing of abscesses and fistulas, use of medical agents, bowel rest, construction of a loop ileostomy and, ultimately, proctectomy.