Sézary syndrome is a rare, usually monoclonal proliferation of T lymphoid cells. We report a case of this form of cutaneous T cell lymphoma with highly probable biclonality of neoplastic proliferation. Biclonality in malignant lymphoma is a rare feature, until now generally reported in B cell lymphoma. Its identification by accurate immunological studies could be of importance since one of the two populations can exhibit a less differentiated phenotype requiring a more aggressive therapeutic regimen than usual. The occurrence of anasarca in our patient was probably due to capillary leak syndrome, already discussed in another case of peripheral T cell lymphoma.