Crude extracts of virus-infected cells labelled with radioactive isotopes were fractionated by ion-exchange chromatography. Virus-specific antigens present in these fractions could be detected by fused rocket immunoelectrophoresis. It was possible to measure the quantitative distribution of 5 HSV type 1 and 10 HSV type 2 virus antigens among 60 fractions. The fractionated antigens were identified by crossed immunoelectrophoresis, using unlabelled reference antigens in the same electrophoretic run. Comparison between the Coomassie brilliant blue picture and the autoradiographic picture of the same plates identified the radioactive-labelled antigens in relation to the reference antigen scheme.