Epstein-Barr virus (EBV) usually infects epithelial cells in the oropharynx and B lymphocytes asymptomatically. Occasionally, however, EBV infects T-cells and natural killer (NK) cells, and infection of these cells has been associated with the development of leukemias and lymphomas. EBV-positive lymphoproliferative disorders of NK cells have been reported with increasing frequency, but the interactions between EBV and NK cells are not fully understood, in part because NK cells are not usually infected with EBV in vitro. The lymphoma-derived EBV-positive NK cell line, YT, has been useful in the study of EBV infection of NK cells. YT cells express the EBV-associated nuclear antigen (EBNA)-1, the latent membrane protein (LMP)-1, and LMP-2A, but not EBNA-2 and LMP-2B genes. This pattern of latent gene expression is compatible with a type II latency program, normally associated with nasopharyngeal carcinoma, Hodgkin's disease, and T-cell lymphoma. In this report, we summarize recent information on EBV-NK cell interactions and EBV-positive lymphoproliferative disorders of NK cells.