Histogenetic classification was applied to 416 cases of human exocrine pancreas carcinoma. Fundamental importance was attributed, in that context, to duct-associated histogenesis. A distinction was, therefore, made between ductal and ductular pancreas carcinomas. Invasive ductal carcinomas were subdivided by three categories: highly stromatous classical adenocarcinoma with poor prognosis, invasive ductal carcinoma with further differentiation (myxoma, squamous carcinoma, pleomorphous macrocellular and parvicellular types), and variations with specific differentiation (serous, mucinous tumours) with good prognosis. Invasive ductular carcinomas were subdivided by terminal non-papillary adenocarcinoma with protracted illness, ciliary adenocarcinoma, microglandular adenocarcinoma, ductulo-acinous tumour with excellent prognosis, and oncocytic carcinoma. These should be distinguished from intermediary cells with cellular transformation and neoplastic differentiation, such as adenocarcinoma with hepatocellular differentiation and mixed tumours (exocrine and endocrine) with alternatingly predominant cell spectra. Determination of prognostically differentiated tumours types is considered to be an indispensable prerequisite for adequately adjusted effective therapy. This appears to be the only approach which promises progress for the future.