Mycosis fungoides (MF) and the Sézary syndrome are a group of extranodal non-Hodgkin's lymphomas of T-cell origin with primary cutaneous involvement. The group distinguishes itself from other primary cutaneous T-cell lymphomas (CTCLs) by its unique clinical features and histopathology. In its early stages, it often resembles common benign dermatoses, and therefore, a definitive diagnosis can be delayed. The affected T cells are characterized by a predominant CD4+ phenotype with frequent loss of CD7 (pan-T-cell antigen) and often demonstrate T-cell receptor (TCR) rearrangement. The prognosis of patients with MF is highly dependent on the extent and type of skin involvement. The initial cutaneous presentation of MF can be patches, plaques, tumors, or erythroderma. Patients who present with limited patch/plaque disease have an outstanding prognosis with an overall long-term survival that is similar to the expected survival of a matched control population. It is exceedingly rare for patients who present with limited or generalized patch/plaque disease without peripheral lymphadenopathy to have extracutaneous involvement. Therefore, the staging evaluation differs for patients with MF versus patients with other non-Hodgkin's lymphomas and should be tailored to the clinical presentation. Patients who have tumorous or erythrodermic skin involvement have a less favorable prognosis, and patients who present with extracutaneous disease have a poor prognosis. There are multiple therapeutic options for patients with MF and the Sézary syndrome. Selection of a specific treatment plan is based primarily on the clinical stage of the disease. The primary therapy for patients with patch/plaque disease without extracutaneous involvement is a topical regimen, whereas chemotherapy or other aggressive systemic regimens are reserved for those with recalcitrant disease or extracutaneous involvement. There is no evidence that early aggressive systemic therapy is preferable to conservative therapy in the management of limited disease. There are newer combination topical and/or systemic regimens that result in an improved clinical response and possibly a prolonged response duration. For advanced disease, standard therapies are often palliative and successful clinical response is often very short-lived. Therefore, all patients with recalcitrant or extracutaneous disease should be considered for newer investigative therapies.