Günter Klöppel is distinguished for many important contributions to the pathology of the pancreas and of neuroendocrine tumours. The majority of these were made at the Department of Pathology of the University of Kiel, which he led for 13 years, after moving from Brussels to Kiel, and developed into a world renowned institution. After his retirement he has continued his scientific activity at the Department of Pathology of the Technical University Munich. His most important scientific contributions were to research on the neonatal nesidioblastosis, the precursor lesions of pancreatic carcinoma and their molecular progression, the description and classification of special pancreatic tumour types, the pathogenesis of alcoholic and autoimmune pancreatitis and the classification of gastroenteropancreatic neuroendocrine tumours. He and his co-workers were the first to investigate the molecular genesis of neuroendocrine pancreatic and duodenal neoplasms in MEN1 patients at the tissue level and to characterise them in detail. On the basis of these studies he developed a hypothesis on the stepwise molecular origin of neuroendocrine tumours from early and atestem cells.