Herpes simplex encephalitis (HSE) is the most important viral encephalitis due to its high mortality and neurological sequelae. The aim of this study was to contribute to better characterise the HSE. We retrospectively analysed patients with a diagnosis of HSE in our hospital during 2000 and 2010. We included those patients who had a positive result for PCR for herpes simplex virus in cerebrospinal fluid and those with a negative result presenting with a consistent clinical and neuroimage profile. We included 26 patients (10 men, 16 women). Mean age was 58 years. Most frequent symptoms at admission were fever, confusion, aphasia and seizures. Mortality rate was 11 %. 2 patients presented a clinical relapse. In conclusion, the most frequent neurological sequelae were aphasia and amnesia. Disorientation, hyponatremia and abnormalities in initial brain CT were identified as new prognostic factors.