We describe a case of synchronous splenic marginal zone-cell lymphoma (SMZL) and T-cell large granular lymphocyte leukemia involving the spleen, liver, bone marrow and peripheral blood. The synchronous occurrence of these two processes was documented by morphological, immunophenotypical and molecular (PCR) analyses of all affected tissues. The pathogenetic mechanisms which may be responsible for the concomitant appearance of these two rather infrequent entities in the same anatomic sites are discussed.