Mycosis fungoides (MF), and the associated leukemic variant Sezary Syndrome (SS), are the most common group of cutaneous T-cell lymphomas. MF/SS is a non-Hodgkin's lymphoma of mature, skin-homing, clonal, malignant T lymphocytes that initially presents in the skin as patches, plaques, tumors, or generalized erythema (erythroderma) and can involve the lymph nodes and peripheral blood. Much progress has been made in recent years in understanding the origin of the malignant T cell in MF/SS and the pathophysiology and immunology of the disease. This recent work has made a great impact on diagnosis, prognostication, and treatment. In this review, we survey the MF/SS published literature over the past year and highlight some of the important advances.