Sézary syndrome is an uncommon variant of cutaneous T-cell lymphoma (CTCL) characterized by erythroderma, pruritus, adenopathy, and circulating atypical T-lymphocytes with cerebriform nuclei. The definition of Sézary syndrome can be further refined by including only patients with a circulating peripheral blood population of clonal T-cells. We have evaluated 79 skin biopsies from such a group of 41 erythrodermic patients with circulating Sézary cells and a clonal population of T-cells detected by T-cell receptor-figene rearrangement on Southern analysis of peripheral blood mononuclear cells. Histopathologic features consistent with chronic dermatitis were observed in 26/79 (33%) skin biopsy specimens, emphasizing that a non-specific histologic appearance is common. Evidence of CTCL was lacking in 11/41 patients on biopsy of their erythrodermic skin. The survival of these patients was not significantly different from 30/41 patients in whom skin biopsies revealed changes diagnostic of CTCL, such as a dermal lymphocytic band with atypical lymphocytes (18/79, 23%) or a mycosis fungoides-like infiltrate (30/79, 38%). This study confirms that non-specific cutaneous hlstopathologic findings are common in Sézary syndrome, even when a circulating T-cell clone is present. This stresses the need for peripheral blood genetic analysis and for multiple or repeat skin biopsies in erythrodermic patients when there is high clinical suspicion of CTCL.