The possibility of enhancing the immunogenicity of human lymphoid cells by infection with vesicular stomatitis virus (V.S.V.) was investigated. V.S.V. infected, purified peripheral human lymphocytes, as well as lymphoblastic cells from the R.P.M.I. series 1788 and 7249, were used to raise antilymphocyte sera in rabbits. The sera were then tested for cytotoxicity and viral neutralization.As compared with uninfected, control lymphoid cells, V.S.V. infection did not enhance the immunogenicity of either type of lymphoid cells. Furthermore, there was no correlation between cytotoxicity and neutralization titers.