BACXBROUND/AIMS: Obstruction of the main pancreatic duct leads to progressive obstructive and atrophying pancreatictis in the cat. The question rematins whether "early" derivative procedures can halt the destructive process or not? METHOODLOGY: Twelve cats submitted to total obstruction of the main pancreatic duct developed chronic obstructive pancreatitis as documented by histopathology. After 5 weeks, five animals underwent a caudal pancreaticojejunostomy. the others served as controls. Pancreatic histoathology underwent a caudal pancreationjejunostomy, the others served as controls. Pancreatic histopathology and ductography was conducted in both groups. as well as tests of endoerine and exocrine functioning. RESULTS: Three of the five cats that underwent a derivation operation died 3-5 weeks following the second operation mainly due to infection, but 2 cats could be followed-up for up to 52 wddks. The bistological signs of inflammation and early fibrosis gradually disappeared and the pancreas returned to normal as assessed by histology, radiology and pancreaticfunction tests. In contrast, cats not submitted to the derivation proceduredeveolped an atrophic chronic pancreatitis. CDHLUSIONS: A ddwobstustive operation, carried out 5 weeks after total obstruction of the main panceratic duct in cats: can halt the progrssion of chronic obstructive pancreatitis and leads to retitution of the pancresa as assessed by histology, radiology and function tests.