Mycosis fungoides (MF) and the Sézary syndrome (SS) are non-Hodgkin's lymphomas with a T-cell phenotype, which have cutaneous involvement as their predominant feature. These disorders are becoming more common, and the patients are frequently being referred to medical oncologists for assistance in management. The development of advanced laboratory techniques, such as molecular genetics and cell-surface phenotyping, has greatly enhanced our understanding of their pathogenesis and may lead to identification of responsible etiologic factors. A myriad of treatment options have been investigated including topical approaches, systemic chemotherapy, and external radiation. Currently, extensive trials are underway examining the potential benefits of agents such as the interferons, interleukin-2, monoclonal antibodies, the retinoids, 2-chlorodeoxyadenosine, and other novel biologic response modifiers or chemotherapeutics. Although all these therapies have benefit in phase II trials, few randomized comparative trials have been performed to identify optimal therapies. Performance of such trials should now become a priority.