Two women with myotonic dystrophy underwent dipyridamole thallium-201 (201Tl) myocardial perfusion imaging, after which one patient developed flat T waves in lead I and aV(L), and inverted T waves in leads V(2-6). The other patient developed a nonspecific intraventricular block that progressed to complete left bundle branch block and was associated with chest discomfort. Reversible scintigraphic defects were observed in both women. Although there was evidence that suggested myocardial ischemia on the ECG changes and 201Tl scintigraphic findings, coronary angiography demonstrated no significant stenoses in either patient. These findings suggest that microvascular dysfunction may lead to myocardial ischemia and conduction disturbances in patients with myotonic dystrophy.