The gene of the major membrane antigen (gp250/350) of the Epstein-Barr virus (EBV) was isolated and inserted under the control of the SV40 early promoter into a eukaryotic expression vector, which allows selection for dhfr+ phenotype. Following transfection with this vector, Chinese hamster ovary cells express on their surfaces proteins immunologically similar to the major EBV membrane antigen. The transcript encoding gp250/350 is processed by partial splicing similarly but more efficiency than in B95-8 cells from which the DNA originates.