Waldenström's macroglobulinemia (WM) is a rare monoclonal gammopathy. Its clinical signs and symptoms include fatigue, weakness, hepatomegaly, splenomegaly, lymphadenopathy, and neuropathies. Patients with WM have a circulating tumor marker, the monoclonal immunoglobulin M protein. High levels of this protein can produce hyperviscosity syndrome, which often is characterized by bleeding from the mucous membranes of the nose and mouth. Asymptomatic patients with WM usually are not treated. Treatment of symptomatic patients and patients with relapsed WM may include alkylating agents, particularly chlorambucil; purine nucleoside analogs, such as fludarabine and cladribine; and, most recently, the use of rituximab. With knowledge about this unusual disease, oncology nurses can provide better care and education for patients with WM.