Recent reports have suggested that plasma concentrations of inorganic sulfate may be lower in patients with Alzheimer's disease (AD). We measured sulfate concentrations in 10 patients with AD and found an average concentration of 0.28 mM, which was not significantly different from the mean concentration in age-matched controls (0.32 mM) or young healthy controls (0.27 mM). These results indicate that plasma sulfate concentrations are not altered in AD and that previous reports suggesting altered metabolism of sulfur-containing xenobiotics in neurodegenerative diseases should be reevaluated.