BACKGROUND: Surgery for rectal cancer is associated with high morbidity and mortality rates. The reason for this has been much debated. This population-based study reports the findings on postoperative morbidity and mortality after rectal cancer surgery following the introduction of a centralized colorectal unit in a county central hospital, supervised by a colorectal surgeon using the most recent techniques. METHODS: All consecutive patients with rectal cancer who underwent surgery at four county hospitals in the Västmanland county in Sweden during 1993-1996 (n = 133) were compared with patients who underwent surgery at the new colorectal unit in the county central hospital from 1996 to 1999 (n = 144). RESULTS: The number of operating surgeons was reduced from 26 to four. The postoperative mortality rate decreased from 8 to 1 per cent (P = 0.002) and the total postoperative complication rate was reduced from 57 to 24 per cent (P