In Argentina, 1488 native taxa are reported with different medicinal properties (Barboza et al., ined.). The 45 % of them grows in Central Argentina (Barboza et al., Flora Medicinal de la Provincia de Córdoba (Argentina): 1. 2006) where is used mostly in folk medicine. Adulteration is frequent in the medicinal ferns used as herbal drugs (Luján, Blacpma 6: 376. 2007.); thus, we decided to study the most relevant epidermal characters with two objectives: 1) to contribute to the differentiation of some closely related taxa, and 2) to obtain information for an adequate quality control of the commercial samples. The epidermis of 29 medicinal ferns has been analyzed. Peeling and cross sections have been made after D?Ambrogio de Argüeso (Manual de Técnicas en Histología Vegetal: 1. 1986). For each species, an epidermal description of leaves and stems with illustrations and photomicrographies is shown. A key with the differential characters is also provided. Trichomes (hairs and scales), ventilating structures (stomata; lenticels; pneumatophores: pores or lines), are highly variable and have taxonomic importance (Rolleri, Revista Museo La Plata, n.s. 14: 65. 1984; Ponce, Darwiniana 28: 317.1987). Non-glandular hairs (simple, bifurcate, branched, dendritic) and different types of scales (deltate, lanceolate, subulate; basifixed or peltate; glabrous or pubescent) are the most common features. Other significant characters are the secretion structures (glandular hairs, mucilaginous cells, nectaries, glands secreting farina). In some groups, the indusium (shape, size, pubescence) provides diagnostic characters at different taxonomic levels. As a conclusion, we put in evidence the importance of the epidermal characters in the delimitation of the taxa, and in the authentication of the commercial samples when quality controls are required. The authors are very grateful to Secyt-UNC for financial support.