A volumetric magnetic resonance imaging assessment of the hippocampal region was done in 50 patients with Alzheimer-type dementia and 25 members of a control group. There were no significant volumetric differences between the right and left hippocampi. The volumetric hippocampal measurements were 39.4% smaller in dementia of the Alzheimer type than in controls. In the differentiation between the analyzed groups of patients, the method had a sensitivity of 95% and a specificity of 92%. A correlation of the hippocampal volumes with the severity of the dementia and the patient's age was found. The results confirmed the importance of hippocampal atrophy in the etiology of dementia. In vivo the quantitative assessment of the hippocampal formation is a valuable tool in the diagnosis of Alzheimer's disease.