Duodenal and gastric ulcers are associated with gastric Helicobacter pylori infection in 92% or 73% of the patients, respectively. Without eradication, the relapse rate after one year is about two thirds for duodenal ulcers and more than 50% for gastric ulcers. Successful eradication of Helicobacter pylori reduces the relapse rate to 0-6%. These data confirm the importance of an infectious agent in peptic ulcers. However, only of minority of Helicobacter pylori infected subjects develop an ulcer. Besides predisposing physical factors, chronic psychosocial stress is a weil documented ulcerogenic co-factor. Several interactions between stress and Helicobacter have been suspected to be involved in ulcer formation, and some of them are supported by preliminary empirical data. Acute psychological stress has also been associated with increased risk of gastric ulcers. Like a solely infectious concept, purely psychogenetic models of ulcer development as weil run the risk of reductionism. lnstead, every single patient needs individual assessment of infectious, somatic, and psychosocial risk. This biopsychosocial risk assessment offers the opportunity of individualized treatment, including psychotherapy in certain patients. However, the effect of individualized psychotherapy in ulcer treatment still needs to be evaluated in systematic intervention studies.