Six mature Bagarus Bayad (Bagrid catfish) of an (average weight of 150 g) were used in this study. Skin samples were taken from the head, trunk, and tail regions and processed for light and electron micro scopy. Light microscopy showed small suprabasal solitary and/or aggrega ted distribution of lymphocytes. These cells had mature compact nuclei and were PAS-negative. Apparantely, there was a tendency of these cells to increase in the trunk rather than the head or the tail region. Electron microscopy showed the presence of intraepithelial lymphocytes with sparce cytoplasmic organells. Their nuclei had thick chromatin clumps arranged along the inner side of the nuclear membrane. The significance of these results has been discussed.