A number of techniques for extraction of DNA prior to polymerase chain reaction (PCR) amplification of herpes simplex virus (HSV) DNA in cerebrospinal fluid (CSF) were compared to the use of "native" CSF in the PCR reaction. The results indicate that extraction of DNA (which allows efficient removal of inhibitors of Taq polymerase) is an essential pre-requisite of the PCR detection of CSF HSV DNA.