A method has been developed for the rapid isolation of herpes simplex virus DNA analogous to miniprep methods for bacterial plasmid isolation. Infected Vero cells are lysed with three freeze-thaw cycles, and the nuclei are removed by centrifugation. DNA is released from the virions in the supernatant by proteinase K digestion. Then the DNA is extracted with phenol/chloroform and precipitated with ethanol. This method requires only small amounts of infected cells as a source of viral DNA, does not use radioactivity, and routinely produces DNA of sufficient purity to be used for restriction fragment length polymorphism (RFLP) analysis on ethidium-stained gels.