Balloon dilatation of the left colon using a Foley catheter was performed in 26 patients prior to staple anastomosis. A 28-mm stapler was then used in six (23%) patients, a 29-mm in seven (27%), a 31-mm in eleven (42%) and a 33-mm in two (8%). Two anastomoses failed (7.9%) and one patient developed local recurrence. None of the remainder developed a symptomatic stricture. Flexible sigmoidoscopy was performed on 18 patients at least 3 months after surgery, revealing that one (5.5%) had developed an asymptomatic stricture. A 28-mm stapler had been used in this case. This technique of dilating the left colon with a Foley catheter is a useful aid to staple anastomosis in large bowel surgery.