BACKGROUND/AIMS: The aim of this study was to investigate the role of cerebrospinal fluid beta-amyloid(1-42) levels and auditory event-related potentials (AERPs) in the progress of mild cognitive impairment (MCI) to Alzheimer's disease (AD).METHODS: In 53 MCI patients, lumbar puncture was performed and beta-amyloid(1-42) levels were determined. Twenty patients were reexamined after 11 months. During this period, 5 of them progressed to AD. Neuropsychological and ERP analyses were performed on all patients during both baseline and endpoint examinations.RESULTS: Compared to stable MCI patients, those that progressed to AD had significantly lower beta-amyloid(1-42) levels (Mann-Whitney test, Z = -2.952, p = 0.003; effect size r = -0.41) and significantly prolonged N200 latencies (Mann-Whitney test, Z = -3.561, p < 0.001, effect size r = -0.49). From ERP variables, only the N200 latency significantly correlated with beta-amyloid(1-42) levels (baseline examination: r(s) = -0.421, p = 0.002; follow-up examination: r(s) = -0.574, p = 0.008).CONCLUSIONS: The combined use of these two parameters enabled discrimination of stable MCI patients from those who developed AD, with 100% sensitivity and specificity. Therefore, this method could be of high diagnostic value for the early diagnosis of AD.