The majority of patients with Chediak-Higashi syndrome (CHS) develop a lymphoproliferative disorder during the accelerated phase of the disease. Controversy exists regarding the benign versus malignant nature of this cellular proliferation. For the first time, we have characterized the immunologic cell markers on the cellular infiltrate in a lymph node from a patient with CHS. The infiltrate was composed almost entirely of T cells, with histopathologic features consistent with a non-Hodgkin's T-cell lymphoma.