en Infectious Diseases Infectious Diseases Original Article Original Article Abstract Background: The etiology of fever of unknown origin (FUO) may differ from different countries. This study was conducted to evaluate the etiology of FUO in patients attending SKIMS, a tertiary care teaching hospital, at Srinagar, Kashmir, India. Methods: From July 2010 to September 2012, this study was done to examine the profile of patients with FUO. The classic FUO was defined as three outpatient visits or three days in the hospital without elucidation of cause of fever. Infectious agents, collagen vascular diseases and hematological malignancies as well as other etiologies were investigated when appropriate. The data were collected and analyzed. Results: A total of 91 cases (62 males and 29 females), with age ranging from 16 to 80 years were investigated. The mean duration of fever before hospitalization was 26±4 days. The etiology of FUO was delineated in (66%) of cases, whereas, (25%) remained undiagnosed. Most common group of FUO was that of infectious diseases (44%) followed by collagen vascular diseases and malignancies (12 % each). Amongst the infection group, brucellosis and salmonellosis comprised the majority of cases (25% each). Conclusion: Infections are the most common cause of FUO followed by collagen vascular diseases in our region. Fever of unknown origin, Classical, Infectious diseases, Collagen vascular diseases 35 39 http://caspjim.com/browse.php?a_code=A-10-1-9&slc_lang=en&sid=1 Tanveer Mir 1003194753284600202 1003194753284600202 No - Department of Medicine, Division of Infectious Diseases, sheri-Kashmir Institute of Medical Sciences, India. Gulam Nabi Dhobi 1003194753284600203 1003194753284600203 No Department of Medicine, Division of Infectious Diseases, sheri-Kashmir Institute of Medical Sciences, India Ajaz Nabi Koul ajazkoul@yahoo.com 1003194753284600204 1003194753284600204 Yes Department of Medicine, Division of Infectious Diseases, sheri-Kashmir Institute of Medical Sciences, India. Tajamul Saleh 1003194753284600205 1003194753284600205 No Department of Medicine, Division of Infectious Diseases, sheri-Kashmir Institute of Medical Sciences, India.