Mollaret meningitis is a rare disease characterized by recurrent and self-limited episodes of aseptic meningitis. It is considered a disease with benign etiology and it has been related to viral infections: Epstein-Barr virus and herpes simplex virus (HSV), type 2 most frequently. Herpes simplex 1 virus has been rarely isolated in the cerebrospinal fluid in patients with Mollaret meningitis; to this end culture, expansion with PCR, and inmunoblot has been utilized. In this article a case of Mollaret meningitis related to type 1 HSV is described. The interest is the demonstration of the herpes simplex virus type 1 within the cytoplasm of the Mollaret cells with a immunohistochemical technique (ABC-peroxidase method) using monoclonal antibodies anti HSV-1 in order to support the diagnosis, being this the first case described in the literature.