Chronic intoxication with dimethylnitrosamine (D.M.N.A.) in the rat induced an experimental cirrhosis which seems stable in time. The intoxication was done by forcible feeding either with 7 or 8 mg/kg of D.M.N.A., three consecutive days a week, for 9 weeks. Chronical intoxication resulted in 50% of hepatic cirrhosis in the 7 mg/kg group and 63% in the 8 mg/kg group. --The diagnostic of hepatic cirrhosis was done by pathological study on the left lobe. --In all cirrhotic rats, verified by histology, biological test were disturbed in a significant way, compared to untreated rats, but not to non cirrhotic intoxicated rats. There was no correlation between pathological anatomy and biology. --Cirrhosis persists after the intoxication but survival duration is much shorter in the group intoxicated with 8 mg/kg of D.M.N.A. --There was no difference in the constitution of cirrhosis between Wistar and Sprague Dawley strains. Therefore the best procedure to induce cirrhosis in rats is chronical intoxication by administration of 7 mg/kg of D.M.N.A. during 3 consecutive days a week for 9 weeks. Pathological study are the only reliable tests to determine the constitution of cirrhosis.