BACKGROUND: Population-based data on the early postoperative outcome after surgery for gastric cancer are very sparse. We examined the development in the quality of surgery and early postoperative outcomes in Denmark following centralization of gastric cancer surgery and implementation of national clinical guidelines. METHODS: All patients in Denmark who underwent resection with curative intent for gastric cancer between 1st July 2003 and 31st December 2008 in one of five university hospitals were registered in a national database. Data on surgical quality and mortality were obtained from the database and compared with the results from the period before centralization (1999-2003). RESULTS: A total of 416 patients underwent resection in the study period. The risk of anastomotic leakages for the whole period was 5.0% (95%CI; 3.2-7.7) compared to 6.1% (95%CI; 4.3-8.6) before centralization, whereas the 30-days hospital mortality was 2.4% (95%CI; 1.2-4.4) compared to 8.2% (95%CI; 6.0-10.4) before centralization. In addition, the percentage of patients with at least 15 lymph nodes removed increased during the study period from 19 in 2003 to 76 in 2008. CONCLUSIONS: Centralization of gastric cancer surgery in Denmark and implementation of national clinical guidelines monitored by a national database was associated with improvements in surgical quality and substantially lower in-hospital mortality.