We studied initial myocardial uptake and myocardial clearance of 123I-metaiodobenzylguanidine (MIBG) in patients with ischemic heart disease of left ventricular dysfunction and dilated cardiomyopathy. Eleven patients with ischemic heart disease of left ventricular dysfunction (IHD group), 6 patients with dilated cardiomyopathy (DCM group) and 7 control cases (control group) were studied. Heart to mediastinum activity ratio (H/M) of early and delayed image was significantly lower in the IHD and DCM groups than in the control group. Although initial myocardial uptake of MIBG showed no significant difference among three groups, myocardial clearance of MIBG was significantly higher in the IHD (35 +/- 11%) and DCM (48 +/- 13%) groups than that in the control group (19 +/- 10%). H/M of delayed image was related to the left ventricular size, initial MIBG uptake and MIBG myocardial clearance. Negative correlation was observed between MIBG myocardial clearance and left ventricular ejection fraction in all cases. In conclusion, initial myocardial uptake of MIBG were not decreased in patients with IHD and DCM. Enhanced myocardial clearance of MIBG was observed not only in patients with DCM but also in patients with IHD.