Abstract: In this paper, OKT6-positive cells in 9 cases of mycosis fungoides (MF) were observed in situ using immunofluorescence technique. In the epidermis of MF lesions dendritic OKT6-positive cells distributed irregularly. Focally increased numbers of OKT6-positive cells were seen in some areas, but their numbers decreased in the areas where the epidermis was atrophic, liquefacted, or destroyed. Beneath these areas more OKT6-positive cells were seen. Some of them showed a variety of changes in their shape, even disintegrated into debris. Also in Pautrier's micro-abscess various amount of dendritic OKT6-positive cells were identified. In the upper dermis of MF lesion a number of OKT6-positive cells were revealed. Some of them aggregated in clusters. In the lymph node section, many OKT6-positive cells were found, but some of them were round or ovale in shape and without dendritic process.