Mantle cell lymphoma is included in the World Health Organization classification as distinct lymphoma subtype characterized by the t(11;14)(q13;q32) translocation, which results in overexpression of Cyclin D1. The clinical presentation often includes extranodal involvement, particularly of the bone marrow and gut. The prognosis of patients with mantle cell lymphoma (median overall survival, 3-5 years) is poorest among B-cell lymphoma patients, even though a prospectively difficult to identify subgroup can survive for years with little or no treatment. Conventional chemotherapy is not curative but obtains frequent remissions (60%-90%) which are usually shorter (1-2 years) compared with other lymphoma entities. Very intensive regimens, including autologous and allogeneic stem cell transplantation, seem required to improve the outcome, but with the median age of diagnosis being 60 years or more, such approaches are feasible only in a limited proportion of patients. The possibility of treating patients based on prognostic factors needs to be investigated prospectively.