Context: Acute Encephalitis Syndrome(AES) caused by viruses is a matter of concern.Japanese Encephalitis(JE) is considered to be the major cause of AES in India but non JE viruses such as Herpes Simplex Virus(HSV) contribute significantly towards the causation of AES.Studies on HSE in West Bengal is limited. Aim:The present study is designed to find out the patient profile and burden of HSV encephalitis among patients suffering from AES in Kolkata and surrounding districts.Study Design: The present study is a descriptive observational study.Study Settings:The present study was undertaken at Virology Unit,Microbiology Department,School Of Tropical Medicine,Kolkata from March 2017–March 2018.Subjects and Methods: Cerebrospinal fluid (CSF) was collected from 120 suspected AES patients and was tested for HSV–1 DNA by RealTime RT PCR using specific primers and probes for Herpes Simplex Virus –1.Results:Out of the 120 suspected cases 6(5%) were found to be positive for HSV–1 DNA in their CSF.The Male:Female ratio of infection was 1:1.A bimodal age distribution was noted and positive cases were found mostly from December to June.All the positive cases had a duration of illness of 5 to 15 days.Conclusion: The burden of HSV–1 infection among patients of AES is 5%.Real Time PCR for HSV–1 DNA in CSF becomes positive within 2 weeks of onset of AES.Therefore, testing of HSV–1 DNA in CSF of suspected patients should be done preferably within 2 weeks of onset of symptoms.