In this study we examined the cytostatic compounds 5 FU and FUDR which are most frequently used in regional chemotherapy for any incidence of hepatobiliary toxicity in animals. For this we compared the intraarterial as well as the intraportal application. Differences between the treatment groups were found in the biliary extraction of these two cytostatic agents. The quantity of metabolites in the bile which could be proven by the MR-spectroscope was highest following intraarterial FUDR infusion, but strong deviations were found in individual cases. A correlation of these findings with the observed frequent hepatobiliary side effects could not be found. It could be shown that the rate and severity of chemical hepatitis and lymphocytic infiltrations in the periportal fields of the liver has no connection to either the cytostatic agent used nor the application form used. Although a sclerosing cholangitis could only be seen in intraarterial therapy. In these cases both cytostatic agents under observation were found to be responsible for this effect in the examined animals. The incidence of sclerosing cholangitis during regional chemotherapy of liver metastases with fluoridised pyrimidines seems to be contingent on multiple factors such as circulation disturbances in combination with drug toxicity.