Purpose: To determine whether the contrast agent Mn-HPTA has potential for detecting differences in myocardial blood flow. Materials and Methods: R1 in the myocardium was calculated from MR signal intensity measurements in 18 pigs after intravenous injection of 5, 15, or 25 µmol MnHPTA/kg body weight. Measurements were made in each animal after administration at rest and during dobutamine-induced stress. Results: A difference of approximately 0.1 sec -1 in the R1 increase between rest and stress still remained 31 minutes after administration of 25 µmol MnHPTA/kg body weight. When two consecutive MnHPTA injections were performed, the second injection induced a lower R1 increase than the corresponding first injection. Conclusion: MnHPTA at a dose of 25µmol/kg body weight (b.w.) has the potential to detect perfusion differences in myocardium. When two consecutive injections of MnHPTA were administered, the R1 change after the second injection was affected by the earlier administration. Therefore, a protocol including more than one administration is not ideal for this contrast agent. © 2006 Wiley-Liss, Inc.