BACKGROUND Acute bacterial meningitis (ABM) and herpes simplex type 1 (HSV-1) encephalitis are two rare but serious infections affecting the central nervous system (CNS). Concurrent bacterial and viral CNS infection has occasionally been reported. OBJECTIVE To illustrate the possibility of intrathecal infection with both Streptococcus pneumonia and HSV-1 by presenting a case and to examine whether herpesvirus reactivation is common in ABM. METHODS We report a case diagnosed with HSV-1 reactivation in the cerebrospinal fluid (CSF) during treatment for pneumococcal ABM. A retrospective analysis of CSF samples from 21 patients with ABM was performed, with analysis of DNA from HSV-1 and four other neurotropic herpesviruses. RESULTS All 21CSF samples were negative for HSV-1, HSV-2, varicella zoster-virus, Epstein-Barr virus and human herpesvirus 6 DNA by PCR. CONCLUSIONS Although herpesvirus infection does not seem to be a common phenomenon in ABM we suggest that HSV-1 reactivation could be kept in mind if patients with ABM show symptoms or signs compatible with encephalitis.