Background and Purpose: This study investigated changes in the severity of gastric metaplasia (GM) of the duodenal mucosa before and after ulcer healing and Helicobacter pylori eradication. It also investigated whether deformity of the duodenal bulb affects the severity of GM and the likelihood of ulcer recurrence., Methods: Eleven patients were consecutively enrolled in this study. They all had duodenal ulcer(s) and H. pylori infection, for which they had received anti-H. pylori triple therapy during the active ulcer stage, and had all undergone serial endoscopic examinations during both the active ulcer and scarring ulcer stages, and at 1 year after ulcer healing. Duodenal biopsies were obtained at each endoscopy to identify the severity of GM. Duodenal ulcers were divided into three types by bulbar shape and GM was classified into four grades of severity., Results: All 11 patients had increased GM severity just after ulcer healing. The 1-year follow-up study revealed that the GM was unchanged in six of eight patients with grade 3 GM severity at the scarring stage, while in the other two it regressed to grade 1 or 2; these two patients suffered ulcer recurrence. A markedly deformed bulb (type III) was found in three patients, of whom two had ulcer recurrence., Conclusion: Two characteristic conditions were found in patients with duodenal ulcer recurrence after H. pylori eradication: a markedly deformed bulb with grade 3 GM at the scarring stage, and a change in GM from high to low grade at or around the previous ulcer site after ulcer healing.