Lymphoproliferative disorders (LPDs) result from the dysregulated production of lymphocytes and include polyclonal benign and monoclonal malignant conditions. LPDs occur in immunocompromised hosts and are sometimes observed in children with primary immunodeficiency. The Epstein-Barr virus (EBV) infects B cells, which are immortalized, and thus EBV-associated B-cell LPD is frequently observed. X-linked lymphoproliferative syndrome (XLP) is a prototype of hereditary EBV-LPD, but XLP-like diseases have recently been reported. They include ITK deficiency, CD27 deficiency, MAGT1 deficiency, STK4 deficiency, coronin-1A deficiency, activated PI3K syndrome, CTPS1 deficiency, autoimmune lymphoproliferative syndrome, and chronic active EBV infection. These diseases are clinically characterized by hemophagocytic lymphohistiocytosis, chronic EB viremia, lymphoma, and dysgammaglobulinemia. Some diseases are associated with a diminished number of invariant NKT cells, which play an important role against EBV infection. EBV-LPD is observed only in humans, and the study of hereditary EBV-LPD will lead to the understanding of human immunology.