AbstractThe effect of portal diversion by ameroid constriction was studied in the carcinogenic process in the rat after initiation of foci by diethylnitrosamine and after the establishment of putative preneoplastic nodules. Portal diversion or portal diversion plus partial hepatectomy did not act to promote or select for the development of nodules. Furthermore, portal diversion did not alter the natural history of established nodules. These results suggest that vascular factors are not important at these early stages of the carcinogenic process in the rat liver.