Clinical symptoms, course of disease, cerebrospinal fluid (CSF) and cranial CT of 53 patients suffering from acute or subacute encephalitis were evaluated retrospectively. The virus could be identified in 21 (39%) patients. Nine of them had herpes simplex virus-encephalitis. 16 patients, eight with herpes simplex virus-encephalitis, died due to the disease. Complete restitution could be observed in 73% of survivors. Disturbance of consciousness and severe focal neurological deficit worsened prognosis towards letality and functional recovery. Most patients had initially elevated number of cellular elements and/or pathological protein concentration in CSF. CSF protein profile showed disturbance of blood-CSF-barrier function in a great number of patients during the first week of the disease whereas autochthonous production of immunoglobulin G was observed predominantly during the second and third week. Elevated concentration of CSF-lactate was seen in herpes simplex virus-encephalitis and in letal cases. 28 (53%) patients had pathological CT-findings. Generalized brain edema, focal hypodensities, focal and cortical contrast enhancement and hemorrhagic imbibation were observed. With one exception patients with herpes simplex virus-encephalitis had hypodense lesions in the temporal lobe. Besides this CT-findings did not allow conclusions regarding the etiology of encephalitis. Prognosis of encephalitis caused by other than herpes simplex virus was worse in case of pathological CT.