Whether diabetic heart muscle disease is related to cardiac ischemia or autonomic neuropathy was investigated employing thallium-201 and [ 1 2 3 I]meta-iodobenzylguanidine (MIBG) myocardial scintigraphy. Among ischemic hearts, displayed by Tl-201 scintigraphy, a distinctly dilated and hypokinetic left ventricle could not be detected. In autonomically denervated hearts, however, well demonstrated by MIBG imaging, distinct dysfunction was found. But, even in these hearts, interacting effects of some concomitant complications could not be excluded.