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Abstract: Diabetic cardiomyopathy shows ECG alterations related to cardiac repolarization and manifested by increased duration of QT interval. Although the mechanism is unknown, it is widely believed that the reduction of hyperglycaemia might prevent such alterations. To test this hypothesis, we used the standardized extract of French pine bark – Pycnogenol® (PYC) with hypoglycaemic and antioxidant properties in 8–9 week old rats with experimentally (streptozotocin) induced diabetes mellitus (DM). PYC was administered orally for 6 weeks in three different doses (10, 20, and 50mg/kg b.w., resp.). Experimental DM was manifested by hyperglycaemia (four to six-fold increase in plasma glucose concentration; p <0.05) and significantly increased mean arterial blood pressure (by 19%; p <0.05) measured using catheterization of carotid artery in vivo. Both abnormalities were dose-dependently reduced by PYC. In addition, diabetic cardiomyopathy was associated with a significant increase in left ventricular weight to body weight ratio (by 21%; p <0.05) and a significant decrease of the width of cardiomyocytes (by 23%; p <0.05) indicating cardiac edema on the one side, and hypotrophy of cardiomyocytes on the other. Both of these changes were not affected by PYC. Consequently to metabolic and hemodynamic alterations, significant prolongation of QT interval (by 20%; p <0.05) was present in diabetic rats, however, PYC failed to correct it. Conclusively, PYC fails to correct QT prolongation in spite of dose-dependent reduction of glycaemia and high blood pressure in streptozotocin-induced diabetic cardiomyopathy. [Copyright &y& Elsevier]