Postmortem findings point to significant abnormalities in central noradrenergic function in Alzheimer's disease (AD) which may be associated with changes in peripheral markers. In this study, the relationship between the peripheral noradrenergic marker, plasma 3-methoxy-4-hydroxyphenylglycol (MHPG), and clinical symptoms was examined in 23 patients with probable AD. Basal MHPG levels correlated significantly with increased cognitive impairment (r = .58, p = .005), controlling for age, age at onset, gender, and time interval between plasma MHPG determination and cognitive testing. These results suggest that plasma MHPG increases as cognitive function in AD deteriorates, further supporting preliminary evidence for increases in noradrenergic indices in association with disease severity in AD.