Diabetes mellitus as a specific etiological type of disease is a relatively frequent complication of chronic pancreatitis and is found always after total pancreatectomy. It is not clear whether in the frequently profound hypoglycaemias of these patients also increased insulin sensitivity may participate. Data in the literature are not uniform. The objective of the submitted work was to assess the insulin sensitivity in 10 patients with chronic pancreatitis (confirmed by ERCP) and diabetes and to compare them with 10 controls and 10 diabetics type 2 treated by diet matched for age and body mass index. The effect of insulin was assessed by the method of the 3-hour hyperinsulin euglycaemic clamp (insulin level 75 microU/ml, blood sugar level 5 mmol/l) acording to glucose consumption as glucose Mglu, glucose clearance MCRglu and insulin sensitivity index SI. Patients with pancreatic diabetes did not differ from controls and type 2 diabetics resp. as regards fasting insulin, C peptide level and lipid parameters. The groups did not differ as regards the glucagon level. Patients with chronic pancreatitis and diabetes had a lower insulin sensitivity than healthy controls.