Mycosis fungoides is the most common type of cutaneous T-cell lymphoma, which is usually observed in mid to late adulthood. We report 5 cases of mycosis fungoides in children, all presenting as patch- and plaque-stage disease most commonly involving the buttocks. Histologic examination showed in every case the typical features of mycosis fungoides. In 4 of the 5 cases, the infiltrating lymphocytes were characterized by the T-cell phenotype CD3⁺, CD4⁺, CD8⁺; and in 3 cases, a monoclonal rearrangement of the T-cell receptor gamma (TCR-γ) gene was found. Three children received topical PUVA treatment, and the other two were treated with mid-potency topical corticosteroids, resulting in complete clinical remission. A management approach to mycosis fungoides with topical PUVA may be appropriate for children. (J Am Acad Dermatol 2002;47:557-61.)