Adult T-cell leukemia/lymphoma (ATLL) remains an uncommon disorder outside well-defined risk groups. We describe the case of an Iranian woman, who presented with isolated meningeal relapse of diffuse large-cell lymphoma. The malignant cells coexpressed CD4 and CD8 and HTLV-1 seropositivity was confirmed. Despite combination chemotherapy disseminated lymphoma developed. Preterminally the characteristic features of ATLL were noted; hypercalcemia, with normal parathyroid hormone-related protein and vitamin D levels, and peripheral blood leukemic involvement.