A 39-year-old man had acoustic hallucinations for about one year due to chronic alcoholism. He suddenly lost consciousness after suffering from headaches for about four weeks. EEG and CT scan were indicative of a brain tumour but lumbar puncture revealed slight pleocytosis and an immunoglobulin G fraction synthesized within the central nervous system. This secretory fraction contained major portions of locally produced herpes simplex antibodies detectable with a complement fixation test and a recently developed enzyme immunoassay. The patient remained in hospital for only a few days and went back to work after six weeks. To our knowledge this is the first case reported surviving herpes simplex encephalitis outside hospital without impairment of consciousness, confusion or substantial neurologic symptoms. The question remains open, whether the generally severe course of this disease had been modified by the chronic alcoholism. It is obvious that the correct diagnosis would have been missed without lumbar puncture.