The liver plays an important role in the pathogenesis of NIDDM. More importantly to the clinician is the myriad of situations in which the care of the patient with diabetes is affected by or causes an effect to the liver. Patients with underlying diabetes can present with abnormal liver chemistries, which can represent findings as benign as hepatic steatosis or as severe as cirrhosis of the liver. The medications used to treat diabetes can be potent hepatotoxins. Several primary liver diseases are associated with increased risk of the development of diabetes. Epidemiologically, there seems to be a correlation between diabetes mellitus, the most common endocrinologic disease, and hepatitis C, the leading cause of chronic liver disease in the United States. In the management of end-stage liver disease, both cirrhosis and orthotopic liver transplantation promote glucose intolerance and diabetes in a number of patients through various mechanisms including insulin resistance and impaired insulin secretion. These relationships highlight both the importance of the liver as an endocrine organ and the multisystem aspects of the patient with diabetes mellitus.