Objective To evaluate the value of evoked potentials (EP) in diagnoses of minimal hepatic encephalopathy (MHE) for liver cirrhotic patients without overt hepatic encephalopathy (OHE). Methods A blind and self control study was conducted in 114 liver cirrhotic patients without OHE. All patients were tested for MHE by the number connection test-A(NCT-A), digit symbol test (DST), visual evoked potentials (VEP), brain-stem auditoru evoked potentials (BAEP), short latency somatosensory evoked potentials (SSEP), P300 auditory event-related potentials (P300ERP). MHE was identified when the NCT-A or/and DST was abnormal. The positive rate was compared among VEP, BAEP, SSEP and P300ERP for their reliability and validity in diagnosis of MHE. Results Of 114 patients, 60 patients were found with MHE (52. 6%), which was positively correlated with Child-Pugh classifications (r=0. 278, P = 0. 003). The positive rate was found 17.5% in VEP, 29.8% in BAEP, 38. 6% in SSEP and 57. 0% in P300ERP. There was no significant difference in diagnosis of MHE between P300ERP and NCT-A+DST (X2 =0. 432,P = 0. 511). The sensitivity of VEP, BAEP, SSEP or P300ERP for diagnosis of MHE was 13. 3%, 41. 7%, 46. 7% or 73. 3%, respectively, whereas the specificity was 77. 8%, 83. 3%, 70. 4% or 61. 1 %, respectively. The receiver operating characteristic curve revealed that the best sensitivity and specificity for the diagnosis of MHE was P300EERP (area under the curve was 0. 672, 95%CI 0. 572 * 0. 773). The agreement of NCT-A+DST with VEP, BAEP, SSEP or P300ERP was 43. 9%, 61. 4%, 57. 9% or 67. 5%. Conclusions P300ERP is a sensitive and specific method for the diagnosis of MHE. which can serve as a supplement but not instead of NCT-A+DST.