The genus Uncaria Schreber (Rubiaceae) includes species that are widely distributed in tropical areas. The inner bark of the stems and leaves of two native species of South America, Uncaria tomentosa (Willd. ex Roemer & Schultes) DC., and Uncaria guianensis (Aublet) J. F. Gmelin, "cat's claw" are used in either folk medicine or in procuring phytotherapeutic drugs. These species contain about sixty active substances which are being tested widely for possible medicinal value. The following applications are considered: peptic ulcer, rheumatism, tumours, antiinflammatory effect, inflammation, diabetes and as general tonic. Currently, Uncaria tomentosa is in demand as tea, tablets or capsules in more than 30 countries outside Perú, as well as inside the country. Pharmacognosy studies are required to determine the comparative morphoanatomical and micrographic features for identification and quality control purposes. Several microscopic parameters, including phloem fibers, calcium oxalate crystals, starch granules, trichomes, and foliar architecture should be considered. The aim of our work is to analyse comparative morphoanatomical and micrographic features which might provide assistance in the identification, analysis and standardization of Uncaria tomentosa (Willd. ex Roemer & Schultes) DC. and Uncaria guianensis (Aublet) J. F. Gmelin stem bark and leaves in order to obtain phytotherapeutic drugs, and of the crude drug as well.