1. A new canine model of hepatic cirrhosis, created by intermittent, oral administration of dimethylnitrosamine, a specific hepatotoxin, is described. 2. DMNA-induced cirrhosis is stable or progressive after discontinuing the toxin, is associated with significant physiological abnormalities which correlate with severity of histological lesions, and can be produced rapidly. 3. Histological, biochemical, and physiological abnormalities associated with DMNA-induced cirrhosis resemble many features of hepatic cirrhosis in man. Data suggest that this model may be useful in studying other parameters of this complex disorder.