Objective To identify the potential value of event-related potentials ( ERPs ) and electroencephalogram(EEG) in early diagnosis of dementia.Methods From June 2008 to July 2011,113 patients with dementia were recruited fom First Affiliated Hospital of Anhui College of Traditional Chinese Medicine.Meanwhile,100 healthy individuals conducting physical examination at this hospital were collected as the control group.P300 and EEG were measured in patients and healthy controls.Results ( 1 ) Compared with healthy controls,patients with early diagnosis of dementia had significantly longer latency(402.5 ± 37.4)ms vs.( 320.4 ± 23.5 ) ms ;t =19.40 ; P =0.02 ) and lower amplitude of P300 ( 3.76 ± 1.76 ) μV vs.( 5.32 ± 1.38 )μV;t=7.24;P=0.01 ).(2)Significant higher proportionof abnormal EEG cases was found in individuals with dementia (68/113,60.2％ ) than that of participants in the healthy control group(34/100,34.0％ ) ( x2 =13.54,P ＜0.01 ).Specifically,patients with early diagnosis of dementia had significantly higher prevalence of moderate (26.5 ％ [ 18/68 ] vs.5.9 ％ [ 2/34 ] ; x2 =4.85,P =0.02 ) and severe ( 8.8 ％ [ 6/68 ] vs.2.9 ％ [ 1/34 ] ; x2 =1.22,P =0.02 ) abnormal EEG than healthy controls,while there were no significant difference of the proportions of mild or borderline abnormal EEG between the two groups ( P ＞ 0.05 ).Conclusion P300 is an extraordinary objective indicator for early diagnosis of dementia.EEG can provide evidence of impaired brain function for individuals with dementia.