The EBV genome in latently infected lymphoid cells offers an opportunity to follow effects on the transcriptional and translational product clearly distinguishable from those of the host cell genome. Exposure of Akata cells, a human lymphoid cell line latently infected by the EBV genome, to a 50 Hz EMF resulted in an increased number of cells expressing the virus early antigens. This finding provides additional evidence that DNA can be modulated by a magnetic field.