BACKGROUND: In 1996, all colorectal surgery in the county of Vastmanland, Sweden, was centralized to the central District Hospital in Vasterås. A Colorectal Unit was established and modern surgical procedures were introduced. The aim of this study was to analyze the outcome for patients treated surgically for distal sigmoid colonic cancer before and after the centralization. METHODS: Hospital records of all patients with distal sigmoid colonic cancer, treated between 1991-1995, group 1 (n = 64), and 1996-2000, group 2 (n = 82), were studied retrospectively. RESULTS: In group 2, there were fewer reoperations (n = 0) than in group 1 (n = 6; p = 0.005) and the postoperative mortality was lower; one in group 2 compared with five in group 1 (p = 0.047). The amount of lymph nodes examined were higher and the length of distal surgical margin longer in group 2. Curatively treated patients in group 2 had better overall survival compared to group 1 (RR 0.56; 95% CI 0.34-0.93). CONCLUSION: Centralization of colorectal surgery resulted in an improvement of pathologic specimens and a decrease in postoperative reoperations and mortality in patients treated surgically for distal sigmoid colonic cancer. Moreover, the overall survival of curatively treated patients was improved.