13 patients with clinically and histologically verified mycosis fungoides were treated with transfer factor as additional therapy to the hitherto conventional treatment after this had failed. After approximately 3 years, complete remission was present in 3 patients, 4 patients were significantly improved and registered as being in partial remission, while the condition was registered as no change in 3 patients. 1 patient was found worse, 1 patient had died after discontinuation of therapy and 1 patient was out of the study. In this case treatment was withdrawn because of the development of contact urticaria to nitrogen mustard, her basic therapy. The number of T lymphocytes, which was low prior to treatment, increased to normal values during the therapeutic period. During the first year a decrease in serum IgE was noted. The results of the clinical evaluation seem to indicate that transfer factor may be of value as an additional therapeutic agent in mycosis fungoides. Controlled investigations are needed and are in progress.