AIM:Cydooxygenases (COX) are key enzymes for conversionof arachidonic acid to prostaglandins.Nitric oxide synthase(NOS) is the enzyme responsible for formation of nitric oxide.Both have constitutive and inducible isoforms.The inducibleisoforms (iNOS and COX-2) are of great interest as regulatorsof tumor angiogenesis,tumorigenesis and inflammatoryprocesses.This study was to clarify their role in pancreaticadenocarcinomas.METHODS:We investigated the immunohistochemical iNOSand COX-2 expression in 40 pancreatic ductal adenocardnomasof different grade and stage.The results were comparedwith microvessel density and dinicopathological data.RESULTS:Twenty-one (52.5%) of the cases showed iNOSexpression,15 (37.5%) of the cases were positive for COX-2.The immunoreaction was heterogeneously distributed withinthe tumors.Staining intensity was different between thetumors.No correlation between iNOS and COX-2 expressionwas seen.There was no relationship with microvessel density.However,iNOS positive tumors developed more often distantmetastases and the more malignant tumors showed a higherCOX-2 expression.There was no correlation with otherclinicopathological data.CONCLUSION:Approximately half of the cases expressediNOS and COX-2.These two enzymes do not seem to bethe key step in angiogenesis or carcinogenesis of pancreaticadenocarcinomas.Due to a low prevalence of COX-2expression,chemoprevention of pancreatic carcinomas byCOX-2 inhibitors can only achieve a limited success. AIM: Cydooxygenases (COX) are key enzymes for conversion of arachidonic acid to prostaglandins. Nitric oxide synthase (NOS) is the enzyme responsible for formation of nitric oxide.Both have constitutive and inducible isoforms. The inducibleisoforms (iNOS and COX-2) are of great interest as regulators of tumor angiogenesis, tumorigenesis and inflammatoryprocesses. This study was to clarify their role in pancreatic adenocarcinomas. METHODS: We investigated the immunohistochemical iNOS and COX-2 expression in 40 pancreatic ductal adenocardium of different grade and stage. the results were compared with microvessel density and dinicopathological data.RESULTS: Twenty-one (52.5%) of the cases showed iNOSexpression, 15 (37.5%) of the cases were positive for COX-2.The immunoreaction was heterogeneously distributed withinthe tumors.Staining intensity was different between the tumors.No correlation between iNOS and COX-2 expressionwas seen. There was no relationship with microvessel density. However, iNOS positive tumors developed more often distant metastases and the more malignant tumors showed a higher COX-2 expression. there was no correlation with other clinical pathological data. CONCLUSION: Approximately half of the cases expressediNOS and COX-2.These two enzymes do not seem to be the key step in angiogenesis or carcinogenesis of pancreatic adenocarcinomas. Due to a low prevalence of COX-2 expression, chemoprevention of pancreatic carcinomas by COX-2 inhibitors can only achieve a limited success.