Sensory dysfunction following the injury of the inferior alveolar nerve requires objective examination to get a reproducible data and to provide necessary treatment. This study was designed to evaluate if the SEP(somatosensory evoked potentials) of the mental nerve can be used as an objective method for the diagnosis of nerve injury and sensory disturbances. The subjects were nineteen patients ($37.4{pm}11.3$ years old) who had been suffered from sensory disturbance of the unilateral lower lip and mental region for over 6 months after the inferior alveolar nerve injuries confirmed by the microsurgical explorations. The clinical neurosensory tests as SLTD(static light touch discrimination), MDD(moving direction discrimination), 2PD(two point discrimination), PPN(pin prick nociception) and accompanied pain were preceded to electro-physiologic examinations as SEP. The score of sensory dysfunction (sum score of all sensory tests) ranged from 0 to 8 were compared to the latency differences of the mental nerve SEPs. The correlation between clinical sensory scores and SEPs were tested by Spearman nonparametric rank correlation analysis, the differences in SEP latency by Kruskal-Wallis test and the latency differences according to PPN and accompanied pain by Mann-Whitney U test. This study resulted that the difference of the latencies between normal side and affected side was $2.22{pm}2.46$ msec and correlated significantly with the neurosensory dysfunction scores (p=0.0001). Conclusively, the somatosensory evoked potentials of the mental nerve can be a useful diagnostic method to evaluate the inferior alveolar nerve injuries and the change of sensory dysfunction to be reproduced as an objective assessment.