Purpose: Herpes simplex encephalitis (HSE) is an important acute neurologic infection not only because is it the commonest fatal sporadic encephalitis occurring in childhood but also since it is treatable with the antiviral drug acyclovir, and treatment delays are associated with a significantly poorer disease outcome. We aimed to determine clinical characteristics and prognosis of HSE cases reviewed retrospectively from several collaborating centers. Method: We searched hospital archives of the last 10 years for pediatric patients with HSE diagnosis, detection of herpes simplex virus(HSV) DNA in the cerebrospinal fluid by PCR. Clinical information regarding age, sex, underlying disease, clinical symptoms, cerebrospinal fluid(CSF) findings, brain MRI findings, treatment and prognosis was gathered and analyzed. Result: A total of 16 patients (11 males and 5 females; mean age, 5.7 years; range, 1 month ~ 17 years) were included. Most of the patients were neurologically healthy prior to the HSE, except 2 patients were born premature. Most common symptoms were fever(100%), changes in mental status(75%), seizure(75%), headache(25%), and vomiting(19%). In CSF samples, mean leukocytes count was 217.9 /mm3, mean protein levels was 75.8 mg/dL, and mean glucose level was 65.9 mg/dL. The result of positive HSV PCR was 4 patients in HSV PCR, 9 patients in HSV-1, and 3 patients in HSV-2. Brain involvement was detected on MRI in 82%, i.e. frontal(62%), parieto-temporal(92%), occipital(38%), thalamus(38%), brainstem(7%), and cerebellum(7%). One third of patients showed normal findings in interictal EEG. All patients were received intravenous acyclovir, mean duration of 22.3 days (range, 13 ~ 35 days). Adjunctively 38% of patients were received intravenous or oral corticosteroid, mean duration of 9.2 days (range, 3 ~ 40 days). Favorable prognosis was observed in 38% of patients, while 38% developed epilepsy and 6% died. Conclusion: The current study demonstrated that a positive diagnosis of HSE should be made by CSF PCR for HSV and brain MRI is the neuroimaging method of choice investigating HSE. We emphasize the importance of early diagnosis and prompt treatment.