Magnetic resonance imaging (MRI) can measure transverse relaxation rate (R2) of tissues. Although R2 is increased by tissue iron levels, R2 is not a specific measure of iron. A new method, based on the fact that ferritin (the primary tissue iron storage protein) affects R2 in a field-dependent manner, can quantify tissue iron with specificity by measuring the Field Dependent R2 Increase (FDRI). Using the FDRI method, we compared brain iron stores in frontal white matter, caudate nucleus, putamen, and globus pallidus of five male patients with Alzheimer disease (AD) and eight age and gender-matched normal controls. FDRI values were significantly higher among AD patients in the caudate and globus pallidus. The data suggest that AD may involve disturbances in brain iron metabolism and that the involvement of iron in the pathophysiology of age-related neurodegenerative disorders can be investigated in vivo using MRI.