¹Sakarya Üniversitesi Tıp Fakültesi, Eğitim ve Araştırma Hastanesi, Sakarya, Türkiye DOI : 10.31067/0.2019.228 Harlequin Syndrome is a rare malady of the sympathetic nervous system which is accompanied by unilateral anhydrosis and dull skin of the face, contralateral hyperhidrosis and flushing. It is a benign autonomic dysfunction which becomes more pronounced with environmental and/or emotional stress and generally requires treatment. Although traumatic and degenerative processes lead to the syndrome, mostly there are no etiologic factors. A 42 years-old-woman presented with hyperhidrosis and flushing of unilateral of the face without ocular findings (ptosis, myosis, etc.), in the time of stress and/or thermo-rising. There was no history of trauma or surgery. Magnetic resonance imaging of the brain, cervical spine or thoracal spine were normal. A complaint becomes to the level of interfering with social intercourse/life so the patient was referred to sympathetic ganglion blockage for symptomatic treatment. We present the case to aim or(The aim of presenting this case is to call attention to a rarely encountered case of idiopathic harlequin syndrome. Keywords : Idiopathic, harlequin