Since antiviral chemotherapy is available herpes encephalitis has become of great importance among viral affections of the central nervous system. Five young infants are presented with special problems of this disease and its diagnostic possibilities especially serological and imaging methods (CT scan, nuclear magnetic resonance tomography, ultrasonography of the brain) as well as electroencephalography. Clinical symptoms are very important since all those methods are not sufficient for early diagnosis and prompt onset of antiviral chemotherapy. Herpes encephalitis should be considered after apparent febrile seizures with focal symptoms as well as increasing disturbance of consciousness as manifestation of acute encephalopathy.