We report on 2 composite lymphomas occurring in elderly patients, morphologically characterized by the combination of peripheral T-cell lymphoma (PTCL) unspecified and B-cell small lymphocytic lymphoma. Immunohistochemistry provided objective confirmation of the coexistence of the 2 malignancies, as did molecular biology by revealing clonal T-cell receptor gamma and immunoglobulin heavy chain gene rearrangements. One of the patients had no history of indolent lymphoma either at the personal and family level, whereas the other showed a strong familial predisposition, his mother and sister having suffered from B-cell chronic lymphocytic leukemia. Epstein-Barr virus was detected in the PTCL component of 1 case, but was negative in the other. To the best of our knowledge, the simultaneous occurrence of PTCL unspecified and B-cell small lymphocytic lymphoma is an exceptional event; the possible pathogenetic correlations between the 2 neoplasms are discussed.