We investigated cardiac sympathetic nerve abnormalities using 123I-metaiodobenzylguanidine (MIBG) in patients with and without autonomic failure (AF), presenting mainly with orthostatic hypotension. 123I-MIBG myocardial scintigraphy was performed in 7 patients with AF, in 10 patients without AF and in 5 normal subjects. Absence of myocardial damage was confirmed in all of the subjects using 210thallium scintigraphy and ultrasound. All of the patients with AF and 4 without AF showed extremely diminished MIBG uptake. 123I-MIBG myocardial scintigraphy is generally useful for detecting adrenergic nervous system dysfunction. Possible confounding factors such as drugs or myocardial beta-receptor dysfunction should be carefully eliminated in patients without AF, because false-negative uptake of MIBG may be seen in some of them.