Résumé : A case of peripheral T-cell lymphoma classified, according to the updated Kiel classification, as a large pleomorphic T-cell lymphoma with a high content of reactive histiocytes and blood hypereosinophilia is reported. Light microscopic examination revealed a diffuse effacement of the lymph node structure by large pleomorphic lymphoma cells mixed with eosinophils and many histiocytes, some of them presenting discrete features of hemophagocytosis. The neoplastic cells were CD3, CD5, CD8 and HLA-DR positive but failed to show CD30 antigen. DNA molecular analysis displayed simultaneous rearrangements of the genes coding for the delta chain of the T-cell receptor and for the Ig heavy chain. Increased serum levels of angiotensin converting enzyme and ferritin were found and probably induced by the reactive histiocytes. Immunoassays (ELISA) with antibodies directed against some cytokines and against the Tac peptide (sIL-2R) were performed. They demonstrated high serum levels of sIL-2R and a slight increase in GM-CSF, but neither IL-5 nor IL-3. The association of blood hypereosinophilia and histiocytic hyperplasia with a peripheral T-cell lymphoma is discussed.