Uncaria guianensis (Aubl.) J. F. Gmel. (“cat’s claw”, Rubiaceae) is a plant with potential to treat asthma because of its anti-inflammatory and antioxidant activities. The aim of this study was to evaluate the effects of two extracts of U. guianensis in an animal model of allergic asthma. Balb/c mice were sensitized twice with ovalbumin intraperitoneally one week apart, then challenged with intranasal ovalbumin for three days. Animals were treated with aqueous or hydroethanolic extracts (100 mg/kg) for three days, simultaneously with ovalbumin challenges. Control mice received saline solution on the same days. In vivo bronchial hyper responsiveness, airway and lung inflammation, IgE levels, and total antioxidant capacity were measured. Treatment with the hydroethanolic extract significantly reduced total cell and eosinophil counts in bronchoalveolar lavage, and in vivo bronchial hyper responsiveness. Moreover, U. guianensis hydroethanolic extract significantly reduced interleukin 13 levels in lung homogenate. Total antioxidant capacity and IgE serum levels were not affected with the extract administration. Of note, treatment with the aqueous extract did not elicit significant effects on asthma-like characteristics. Only the hydroethanolic extract of U. guianensis reduced lung inflammation and bronchial hyper responsiveness in asthmatic mice. Key words: Anti-inflammatory agents, asthma, oxindolics, phenols, respiratory hypersensitivity, Uncaria guianensis, Rubiaceae.