Betulinic acid (BA) is a lupane-type triterpene with a number of biological activities already reported. While potent anti-HIV and antitumoral activities were attributed to BA, it is considered to have a moderate antiinflammatory activity. Here we evaluated the effects of BA in a mouse model of endotoxic shock. Endotoxemia was induced through intraperitoneally LPS administration, nitric oxide (NO) and cytokines were assessed by Griess method and ELISA, respectively. Treatment of BALB/c mice with BA at 67 mg/kg caused a 100% survival against a lethal dose of lipopolysaccharide (LPS). BA treatment caused a reduction in TNF-α production induced by LPS but did not alter IL-6 production. Moreover, BA treatment increased significantly the serumlevels of IL-10 compared to vehicle-treated, LPS-challenged mice. To investigate the role of IL-10 in BA-induced protection, wild-type and IL-10−/− mice were studied. In contrast to the observations in IL-10+/+ mice, BA did not protect IL-10−/− mice against a lethal LPS challenge. Addition of BA inhibited the production of pro-inflammatory mediators by macrophages stimulated with LPS, while promoting a significant increase in IL-10 production. BA-treated peritoneal exudate macrophages produced lower concentrations of TNF-α and NO and higher concentrations of IL-10 upon LPS stimulation. Similarly, macrophages obtained from BA-treated mice produced less pro-inflammatory mediators and increased IL-10 when compared to non-stimulated macrophages obtained fromvehicle-treatedmice. In conclusion,we have shown that BA has a potent anti-inflammatory activity in vivo, protecting mice against LPS by modulating TNF-α production by macrophages in vivo through a mechanism dependent on IL-10.