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We measured proton magnetic longitudinal (R1) and transverse (R2) relaxation rates at 1.4T, iron concentrations, water contents, and amyloid plaque densities in postmortem brain tissue samples from three Alzheimer's disease (AD), two possible AD, and five control subjects. Iron concentrations andR1 were significantly higher in the temporal cortex region of our AD group compared to the controls. Frequency analyses showed that the observed trends of higher iron,R1, andR2 in AD gray matter regions were statistically significant. Simple regression models indicated that for AD and control gray matter the iron concentrations and water contents have significant linear correlations withR1 andR2. Multiple regression models based on iron concentrations and water contents were highly significant for all groups and tissue types and suggested that the effects of iron become more important in determiningR1 andR2 in the AD samples. At 1.4TR1 andR2 are strongly affected by water content and to a lesser extent by variations in iron concentrations. The AD plaque density did not correlate with iron concentrations, water contents,R1, orR2, suggesting that increases in AD brain iron are not strongly related to the accumulation of amyloid plaques. Magn Reson Med, 2008. © 2008 Wiley-Liss, Inc.