Following a short summary of the historical development of the terminology, the nosological separation between peptic ulcer disease and secondary ulcers - including the gastroduodenal stress erosions and ulcers - is stressed. The differing and in the last 20 years decreasing frequency of the different causes as well as the pathogenesis - mainly disturbances of the mucosal defense mechanisms (blood supply, mucus secretion and epithelial renewal) - are discussed, partly refering to results of own investigation.