Eight patients with 29 lesions of histologically verified I st stage of Mycosis fungoides were successfully treated by electrochemotherapy with interferon-alpha. For this purpose 8 biphasic pulses were used, each of 50+50 gs duration with 900 gs interpulse intervals, resulting in a burst of 7.1 ms total duration. Compared to the traditional monoimmunotherapy with interferon-alpha applied three times weekly for a total of 4 weeks, the electrochemotherapy was very efficient. Complete response (CR) was observed in 25 (86%) of the 29 treated lesions by single-act electrochemotherapy with interferon-alpha. At the end of the 12-month period, all 29 lesions showed 100% complete response (CR). New lesions for a period of 12 months were not observed. The expected mechanism involved in multiple cytotoxic action of interferon-a could be the local increased concentration in the tumour and prolongation of the time of its action after the application of pulses. (C) 2006 Elsevier B.V. All rights reserved.