A technique for the analysis of EBV antigens in extracts of unlabelled EBV infected cells has been developed. Using this technique we have demonstrated that the EBV early antigen complex consists of several proteins and is not completely expressed in chemically induced Raji cells. Studies with a range of sera from patients with infectious mononucleosis and nasopharyngeal carcinoma have shown that despite similar titers by the indirect fluorescent antibody test different populations of proteins were precipitated by different sera.