Endoanal and endorectal ultrasound have an important role in colorectal surgery. They can be applied in the management of faecal incontinence, rectal tumours and inflammatory perianal conditions. In faecal incontinence, anal ultrasound will confirm the presence or absence of sphincter defects. This will direct any operative intervention such as direct sphincter repair. Ultrasound in rectal cancer allows staging of the tumour by assessing the depth of invasion through the bowel wall and involvement of mesenteric nodes. Such staging might influence the choice of operation and determine which patients might benefit from preoperative chemotherapy and radiotherapy. Ultrasound has a particular role in recurrent and complex anal fistula and perianal sepsis. Preoperative and perioperative planning with accurate delineation of fistula tracts, extensions and sphincter involvement might help prevent recurrence and impaired continence from sphincter damage after surgery. Correct interpretation of ultrasound images requires training and experience so that the results can be properly correlated with the clinical situation.