Background.  Mycosis fungoides (MF) is the most common form of primary cutaneous lymphoma, and is characterized by a malignant proliferation of CD4+ cells. Psoralen ultraviolet A (PUVA) irradiation is the most common treatment for cutaneous lesions. However, PUVA carries the risk of adverse reactions to psoralens and long-term risk of skin cancer. UVA1 may be a safer alternative. Aim.  To assess the efficacy of UVA1 phototherapy in patients with early-stage MF (T1-T2). Methods.  Four patients with early-stage MF were treated with 1630-2710 J/cm(2) UVA1 given in 29-40 fractions, and the effect was assessed by clinical examination and by high-resolution ultrasonography. Results.  Complete clinical remission of MF was achieved in all cases. Conclusions.  This preliminary report indicates that UVA1 phototherapy might be an efficient treatment for early-stage MF.