Objective: To study lexical semantic memory in patients with amnestic mild cognitive impairment (aMCl), mild Alzheimer's disease (AD) and normal controls. Method: Fifteen mild AD, 15 aMCI, and 15 normal control subjects were included. Diagnosis of AD was based on DSM-IV and NINCDS-ADRDA criteria, and that of aMCl, on the criteria of the International Working Group on Mild Cognitive Impairment, using CDR 0.5 for aMCl and CDR 1 for mild AD. All subjects underwent semantic memory tests (Boston Naming-BNT, CAMCOG Similarities item), Rey Auditory Verbal Learning Test (RAVLT), Mini-Mental Status Examination (MMSE), neuropsychological tests (counterproofs), and Cornell Scale for Depression in Dementia. Data analysis used Mann-Whitney test for intergroup comparisons and Pearson's coefficient for correlations between memory tests and counterproofs (statistical significance level was p < 0.05). Results: aMCl patients were similar to controls on BNT and Similarities, but worse on MMSE and RAVLT. Mild AD patients scored significantly worse than aMCl and controls on all tests. Conclusion: aMCl impairs episodic memory but tends to spare lexical semantic system, which can be affected in the early phase of AD.653A619622