Cardiac scintigraphy with meta-[123I]iodobenzylguanidine (MIBG) is used to assess cardiac sympathetic function. We performed [123I]MIBG scintigraphy in 7 patients with neurological diseases presenting orthostatic hypotension and other autonomic failures (AF), 22 neurological patients without AF, and 9 healthy subjects. Thallium scintigraphy and echocardiography were also performed in all subjects. In this series, patients with any evidence of cardiac dysfunction were excluded. No [123I]MIBG accumulation was observed in all patients with AF, and cardiac defects were noted in 7 patients (5 with Parkinson's disease [PD], 2 with spinocerebellar degenerations [SCD]), and in some patients without AF. In contrast, the distribution of [123I]MIBG was normal in all the healthy subjects. No decrease in [123I]MIBG accumulation was resulted from drug therapy (droxidopa, amezinium and thyrotropin-releasing hormone). In conclusion, reduced accumulation on [123I]MIBG scintigraphy may be due to myocardial beta-adrenoceptor dysfunction or reduced central sympathetic activity of the heart, or both.