In the present study, the methanolic extract of Ailanthus excelsa (Roxb) leaves, a plant used in Egyptian traditional medicine was investigated for phytochemical constituents and some biological activities. In vitro: antioxidant activity and in vivo: Lethal dose (LD50) acute and chronic toxicity and anti-nociceptive and anti-inflammatory effects were determined. It was found that methanolic extract of Ailanthus excelsa leaves is nontoxic up to 5 g.kg-1 b. wt in mice. Also rats were given a daily single oral dose of the extract for 7 and 30 successive days for assessment of acute and chronic toxicity. The extract did not induce any significant change in serum levels of ALT, AST, GGT, total protein, albumin, BUN and creatinine as compared with saline control group in rats. The extract exhibited a significant antioxidant, anti-nociceptive activity and no anti-inflammatory effects. Chromatographic separation of A. excelsa  MeOH extract has yielded eleven known flavonoid compounds. Their structures were established on the basis of chromatographic properties and spectroscopic (UV, 1H, 13C NMR, MS) analyses.