A 20-year-old man with Sézary-syndrome is presented. This disease is characterized by a generalized, exfoliative dermatitis, a massive enlargement of the superficial lymph nodes and a leukaemic blood count with atypical cells. Histologically the skin changes were similar to mycosis fungoides, the lymph nodes showing non-specific changes. In the peripheral blood with a leucocyte count of 30.000 atypical monocytoid (7%) and lymphocytoid (30%) cells could be differentiated. Electron microscopy revealed large cells with multilobular nuclei in the skin infiltration as well as in the peripheral blood, classified as ‘Sézary cells’. The Sézary-syndrome is a rare and special form of skin reticuloses.