The authors observed Lhermitte's sign in four patients after bone marrow transplantation (BMT) for hematologic malignancies. Three patients had acute myelogenous leukemia (AML), and one had chronic myelogenous leukemia. Before BMT, the patients with AML received daunorubicin, cytosine arabinoside and etoposide, whereas the patient with chronic myelogenous leukemia received hydroxyurea. One patient with AML received MY-9 antibody-depleted autologous BMT. The other patients received human lymphocyte antigen-identical, allogeneic BMT. Preparative therapy for BMT was cytosine arabinoside, cyclophosphamide, and total body exposure to radiation for two patients, and busulfan, cyclophosphamide, and no exposure to radiation in two other patients. Lhermitte's sign appeared 4 to 8 months after BMT and resolved spontaneously after 2 to 5 months. Neurologic sequelae had developed in none of the patients 16 to 34 months after BMT. No unifying etiologic factor could be identified in these patients. The development of Lhermitte's sign after BMT appears to be a benign, self-limited phenomenon that requires no specific treatment.