This work presents physicochemical and chemical characterization of Equisetum giganteum L. stems, an endemic species of Latin America widely used in the traditional medicine, mainly as diuretic. The loss on drying, total ash and acid-insoluble ash values were 11.85 ± 0.11 %, ≥13.61 ± 0.38 %, and ≥ 9.43 ± 0.35 %, respectively. The total phenolic and flavonoid content were 7.27 ± 0.05 mg GAE/g and 0.42 ± 0.0141 g %, respectively. Data on drying, adsorption and sorption isotherms and other physicochemical determinations are also presented. Thin layer and liquid chromatography profiles revealed the presence of polyphenols. These results will provide important information for future studies involving the standardization and quality control of E. giganteum raw material and products.