Small lymphocytes were identified in a freshwater teleost (Pimelodus maculatus) epidermis at the ultrastructural level. Although they were the most abundant, the medium and the large lymphocytes were also present. They were found at all levels of the epidermis, specially in small spaces between the cells of the basal layer. They appeared in contact only with filament-containing cells. Intercellular junctions, however, were never observed. They were negative to the histochemical test used to detect the present of acid phosphatase.