Primary pancreatic carcinomas were studied histologically and histochemically, to assess the frequency of dutal hyperplasia in tissue adjacent to malignat neoplams. Hyperplaaia waw divided into four types: simple, papillary, atypical and ductular, affecting large, medium and small ducts (ductules). All types of hyperplasia were frequently seen in areas adjacent to carcinomas, including ductal, pleomorphic, mucinous, adenosquamous, small and spindel cell and cystadenocarcinomas. In contrast, acinar cell carcinoma and microadenocarcinoma were less frequently associated with ductal hyperplasia. Mucin histochemistyr revealed differences in types of mucin betwwnd the normal ducts and hyperplastic pancreatic ducts and carcinomas. The former group comtained smal amouts of sulphated mucin while the latter showed a marked increase in neutral and sialomucins. Our study salso suggests that both papillary with the latter showed a marked increse in neutral and sialomucins. Our study salso suggests that both papillary and atypical hyperplasia are precancerous lesions, supporitng and hypothesis of ductal origin of pancreatic carcinomas. And atypical hyperplasia are prcancerous lesions, suporintg and hypothesis of ductal origin of poanereatic carcionmas.