RABBIT kidney and fibroblast cells, after exposure to the isolated DNA of herpes simplex virus in the presence of DEAE-dextran, have been shown to develop a cytopathic effect1. Enhancement of plaque formation with DNA using DEAE-dextran has been described2,3 but a new technique has been recently reported which gives a 100-fold increase in efficiency over the DEAE-dextran method for human adenovirus DNA4. Here we report that using this technique the DNA of herpes simplex virus type I (HSV-I) can be shown to be infectious and plaques can be obtained on BSC-1 cells (African green monkey kidney cells).