Background: Although parch-stage mycosis fungoides (MF) has a generally good prognosis, and long-term survival rates with current therapies UV-B, photochemotherapy, topical nitrogen mustards, electron-beam therapy) are similar, there is concern regarding their potential adverse effects. Narrowband or TL-01 UV-B phototherapy (311 nm), in use for more than 10 years, is more effective than broadband UV-B for the treatment of psoriasis, with an efficacy approaching that of psoralen UV-A. This open study assesses TL-01 as an alternative therapy for patch-stage MF. Observations: Eight white patients (4 men, 4 women, age range, 66-83 years) with histologically proven patch-stage MF received TL-01 phototherapy 3 times weekly using a standard protocol. Complete clearance of MF was achieved in 6 cases in a mean of 9 weeks or 26 treatments (range, 20-37 weeks) and 4 patients have had prolonged remissions. Mean duration of clinical improvement has born 20 months (range, 11-40 months). Partial response to TL-01 or poor histologic improvement was associated with rapid relapse. Conclusions: TL-01 is an effective, convenient therapy that may have less risk of long-term adverse effects than current alternatives. Although larger prospective studies are necessary, For some patients intermittent courses of TL-01 may offer effective long-term therapy.