We report a case of main duct type of intraductal papillary-mucinous tumor (IPMT) with minimal invasion followed-up for eight months after initial diagnosis. A 63-year-old man had been diagnosed with ...IPMT by direct biopsy of the tumor at the tail of the main pancreatic duct under endoscopic retrograde pancreatography (ERP) guidance in June 2001. The patient had refused operative treatment and had followed up as an outpatient for eight months. During this period, he had suffered from recurrent pancreatitis. He admitted again to our institution in order to reevaluate IPMT in January 2002. Computed tomography and ERP demonstrated obvious diffuse dilataion of the whole pancreatic duct. Filling defects due to mucin and also tumor were observed on ERP. A small mass was found in the distal part of the dilated main pancreatic duct. For gaining curative outcome, distal pancreatectomy with splenectomy and lymphoidectomy of 1st and 2nd group was performed. Pathologic findings showed that tumor was located in the tail of the main pancreatic duct, 7mm in size. Minimal invasion to pancreatic parenchyma with maximum depth in 4mm was also confirmed. Differentiation between adenoma and carcinoma, prediction of having invasive nature, and diagnosis of minimal invasion are now clinical challenge.