The investigation on steroidic fraction of Uncaria tomentosa, commonly called Una de gato, showed the presence of beta-sitosterol (60%), stigmasterol, and campesterol. The percentage of sterols have been carried out by GLC. The spectroscopic data 1H-NMR and MS of the three compounds are also reported, with the beta-sitosterol as the main sterol. Preliminary pharmacological investigations prove a moderate antiinflammatory activity.