Background: Headache is among most common reason to seek medical attention on global basis being responsible for more disability than any other neurological problem. In developing world headache was not sufficiently studied previously as a cause of morbidity. In this study clinical and etiological analysis of patients with chronic headache using the third edition of International Classification of Headache Disorder (I.C.D.H–3) in Tertiary care referral centre (A.N.M.M.C, Gaya) Methods: In this study 100 patients included who came with complaints of headache more than 3 months in the outpatient department of Medicine Anugrah Narayan Magadh Medical College Gaya Bihar. Clinical and psychiatric evaluation of patients have done and if needed clinical investigations also done. Results: Out of 100 patients of chronic headache, chronic primary headache (82%) was the most common type, with migraine found in 49% of cases, and tension type headache (23%) were more common primary headache. Other common primary headachesa are New persistent headache, Chronic cluster headache and mixed type (tension +migrain). Chronic headache is more common in females and adolescents. Conclusions: Since chronic primary headache is most common type headache in which Migraine and Tension type headache are common type. Therefore, headache needs proper clinical evaluation and specific treatment for proper management of headache. This study helps in identifying the significant gap in headache care and provide better information for management of headache.