Objcctive To investigate the predictive value of the 40 Hz auditory steady-state response (ASSR) in patients with the malignant process of middle cerebral artery territory infarction.Methods The40 Hz ASSR and brainstem auditory evoked potential (BAEP) were performed within 72 hours after patients with middle cerebral artery terrtory infarction admitted in the neuro-intensive care unite (NICU).At the same time,the National Institutes of Health Stroke Scale (NIHSS) scores were assessed.Multivariable logistic regression analysis was used to deterrmine the influencing factors of the malignant process.The relevant indicators of the malignant process were analyzed by the receiver operating characteristic(ROC) curve in order to clear the predictive value of 40 Hz ASSR in the malignant process of middle cerebral artery territory infarction.Results A total of 104 patients with supratentorial middle cerebral artery territory infarction were included.They were divided into the malignant process group (n=59) or the non-malignant process group (n=45).There were significant differences in the baseline NIHSS scores (17.25 ± 7.23 vs.20.40 ± 8.09; t =- 2.055,P =0.043),infarct volume (105.85 ± 73.37 mm3 us.179.15 ± 144.38 mm3; t =-3.011,P =0.004),leukocyte count ([ 10.26 ±3.14] × 109/L vs.[ 13.45 ±5.42] × 109/L; t =-3.336,P =0.001),40 Hz ASSR (Z =-3.237,P =0.001),and short-latency somatosensory evoked potentials (Z =-3.130,P =0.002) grade between the malignant process group and the non-malignant process group.Multivariate logistic regression analysis showed that the40 Hz ASSR (odds ratio [OR] 3.347,95％ confidence interval [CI] 1.630 -6.872; P=0.014),infarct volume (OR 1.006,95％ CI 1.001 - 1.012,P=0.003),and leukocyte count (OR 1.277,95％ CI 1.074 - 1.402; P =0.001) were the independent predictors in patients with the malignant process of middle cerebral artery territory infarction.When the 40 Hz ASSR was grade 3,the sensitivity and specificity of predicting malignant process were 39.5％ and 94.4％.Conclusions The 40 Hz ASSR has an important predictive value in patients with the malignant process of middle cerebral artery territory infarction.