The root of Aralia cordata is a traditional medicine for the treatment of inflammation, fever, pain, and spasm in the various diseases in Korea. We isolated a dibenzylbutyrolactone diterpene acid, 7-oxosandaracopimaric acid (OSA), from the ether fraction of Aralia cordata MeOH extract, and studied the effect of OSA on phenylquinone (PQ)-induced writhing syndrome and PQ-induced capillary permeability increase, compound 48/80-induced histamine release by peritoneal mast cells, cycloxygenase (COX) activities, and silica-induced RAW 264.7 cell reactive oxygen species production. OSA (30 mg/kg, p.o.) significantly (p < 0.05) inhibited PQ-induced writhes by 25.8% and the PQ-induced capillary permeability increase levels by 33.13% as compared with PQ control. Furthermore, OSA (10 mM) inhibited COX-1 by 22.82 +/- 1.94%, and COX-2 by 15.86 +/- 1.35%, respectively, to the same extent as indomethacin at the same concentration (10 mM). And OSA (3.0 mM) significantly (p < 0.05) inhibited compound 48/80-induced histamine release from rat mast cells, and its activity was similar to that of celebrex (1 mM), but no piracetam (0.1 mM) inhibited them. OSA did not inhibit ROS production in RAW 264.7 cells. These results indicated that OSA has analgesic and anti-inflammatory effects due to its inhibitory effects on capillary permeability, COX activities, and histamine release.