Humoral hypercalcemia of malignancy is a common metabolic disturbance associated with solid tumors, but it also occurs in lymphoma patients. Among these, low grade B-cell lymphoma accounts for only few cases, in which secretion of parathyroid hormone-related protein (PTHrP) remains even exceptional. We report the very rare case of a patient with a CLL type low grade leukemic B-cell lymphoma showing PTHrP-related hypercalcemia without evidence of bone lesions. Using immunohistochemistry, we demonstrate the cytoplasmic expression of PTHrP by the lymphoma cells in the bone marrow obtained at the onset of hypercalcemia. We postulate a pathogenetic role of leukemic cell production and secretion of PTHrP in hypercalcemia in low grade leukemic B-cell lymphoma.