Decreased cardiac uptake of meta-iodobenzylguanidine (MIBG) on [¹²³I]MIBG myocardial scintigraphy has been reported in Parkinson’s disease (PD) and dementia with Lewy bodies (DLB). We hypothesized that cardiac sympathetic denervation might account for the pathomechanism. To elucidate the extent, frequency and pattern of cardiac sympathetic nerve involvement in Lewy body disease and related neurodegenerative disorders, we immunohistochemically examined heart tissues from patients with PD (n=11), DLB (n=7), DLB with Alzheimer’s disease (DLB/AD; n=4), multiple system atrophy (MSA; n=8), progressive supranuclear palsy (PSP; n=5), pure AD (n=10) and control subjects (n=5) together with sympathetic ganglia from patients with PD (n=5) and control subjects (n=4), using an antibody against tyrosine hydroxylase (TH). TH-immunoreactive nerve fibers in the hearts had almost entirely disappeared in nearly all the patients with PD, DLB and DLB/AD, whereas they were well preserved in all the patients with PSP and pure AD as well as in all except for one patient with MSA. In PD, neurons in the sympathetic ganglia were preserved in all except for one patient. Decreased cardiac uptake of MIBG in Lewy body disease reflects actual cardiac sympathetic denervation, which precedes the neuronal loss in the sympathetic ganglia.