The purpose of this study was to investigate myocardial uptake of ¹²³I-metaiodobenzylguanidine (MIBG) in patients with pure autonomic failure (PAF), which has pathologic features in common with idiopathic Parkinson's disease (IPD) and dementia with Lewy bodies (DLB). Six patients with PAF, 130 with IPD, 21 with DLB, 9 with corticobasal degeneration (CBD), 11 with progressive supranuclear palsy (PSP), and 11 with multiple-system atrophy (MSA) underwent myocardial ¹²³I-MIBG scintigraphy, as did 16 control patients. Resulting heart-to-mediastinum (H/M) ratios were significantly lower in patients with PAF, IPD, or DLB than in patients with CBD, PSP, or MSA and in the controls. H/M ratios were lower for delayed images than for early ones in patients with PAF, IPD, or DLB, whereas the ratios were higher for delayed images in patients with CBD and in the controls. Cardiac sympathetic denervation and enhanced washout of ¹²³I-MIBG from sympathetic nerve terminals may develop in parallel in patients with PAF, IPD, or DLB.