Summary White blood cells from a normal adult male regularly became established as continuous lines when cultured in the presence of X-irradiated cells of an EBV-infected line of leukocytes derived from a leukemic girl and a monolayer of human placental cells. Seven of the 9 lines thus established became infected with EBV. The possible role of the various components of the culture system in the observed transformation is discussed. Note added in proof: The TNL line in Expt. 1, which did not demonstrate EBV antigen at the time the manuscript was submitted, showed approximately 0.4% cells with antigen when it was subsequently examined. We are grateful to the Children's Cancer Research Foundation for clinical specimens and to Mrs. A. von Zweck, Miss A. Holloway, Miss E. Grogan, Mrs. I. Irwin and Mrs. E. Lisco for valuable assistance.