Objectives:Hypothalamic-Pituitary-Adrenocortical(HPA) system dysregulation plays an important role in the pathophysiology of major depressive disorder. Medically unexplained somatic symptoms comprised the predominant complaints of korean patients with major depressive disorder. It might be related to dysregulation of HPA system and somatic symptoms. The aim of this study was to investigate the association between Hamilton Depression Rating Scale severity and the Plasma Adrenocorticotropic Hormone(ACTH) & Serum Cortisol level in Korean patients with major depressive disorder. Methods:Our study design was prospective. A total 111 hospitalized patients with major depressive disorder (DSM-IV) at Anam Hospital, Korea University Medical Center between Jan 2009 and May 2011 were selected. Hamilton Depression Rating Scale was measured by psychiatrist. Plasma ACTH, Serum Cortisol levels were analyzed at the time of admission. Results:There are significant correlations(p<0.05) between Hamilton Depression Rating Scale of somatic component(HAM-D 11-15 item) and Plasma ACTH and Serum Cortisol level. However, other HAM-D sub items were not significantly correlated with Plasma ACTH and Serum Cortisol level except somatic component. Conclusion:Our Study results suggest that hyperactivity of HPA axis might be correlation with somatic symptoms in korean patients with major depressive disorder.