OBJECTIVES: The purpose of this study was to quantitatively assess the degree of myasthenia gravis (MG) affecting mental health through the results of multiphasic military personality inventory in late adolescence. METHODS: We collected and analyzed the results of the military personality inventory for healthy controls and MG patients among the 19-year-old men who visited the Military Manpower Administration from February 2007 to January 2010. Military personality inventory invented for Korean military test has similar system to Minnesota multiphasic personality inventory. RESULTS: Among validity scales, each score of faking good, faking bad and infrequency subscales showed no difference between healthy control and MG groups, respectively (t=−0.51, p=0.607 ; t=0.11, p=0.913 ; t=1.41, p=0.158). Among neurosis scales, the score of somatization subscale was higher (t=2.29, p=0.023) in MG group. Among psychopath scales, the score of schizophrenia subscale was lower in MG group (t=−2.38, p=0.018). CONCLUSIONS According to MPI results, we can confirm that MG patients in late adolescence may be more concerned with their somatic symptoms than the control group, and that they may be more likely to abide by the regulation and be conventional in their behavior than the control group.