Mild cognitive impairment (MCI), a major risk factor for dementia, has an amnestic subtype that has a high probability of progressing to Alzheimer's disease. The rate of progression may be predicted by the severity of memory impairment at baseline, the severity of hippocampal atrophy, and, possibly, the presence of an epsilon4 allele of the apolipoprotein E gene. MCI can be diagnosed using purely clinical or a combination of clinical and neuropsychologic criteria. Treatment trials show no disease-modifying effect. The radiologists' role is to determine whether or not the hallmarks of degenerative and vascular disease of the brain are present, aiding in the diagnosis of the cause of MCI.