In our ongoing study to identity antioxidants from natural sources, the antioxidant activity of Nelumbo nucifera stamens was evaluated for their potential to scavenge stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals, inhibit total reactive oxygen species (ROS) generation, in kidney homogenates using 2 ,7 -dichlorodihydrofluorescein diacetate (DCHF-DA), and scavenge authentic peroxynitrites ($ONOO^-$). A methanol (MeOH) extract of the stamens of N. nucifera showed strong antioxidant activity in the $ONOO^-$system, and marginal activity in the DPPH and total ROS systems, so were therefore fractionated with several organic solvents, such as dichloromethane ($CH_2 Cl_2$), ethyl acetate (EtOAc) and n-butanol (n-BuOH). The EtOAc soluble fraction, which exhibited strong antioxidant activity in all the model systems tested, was further purified by repeated silica gel and Sephadex LH-20 column chromatographies. Seven known flavonoids [kaempferol (1), kaempferol 3-Ο-$eta$-D-glucuronopyranosyl methylester (2), kaempferol 3-Ο-$eta$-D-glucopyranoside (3), kaempferol 3-Ο-$eta$-D-galactopyranoside (4), myricetin 3 ,5 -dimethylether 3-Ο-$eta$-D-glucopyranoside (5), kaempferol 3-Ο-$alpha$-L-rhamnopyranosyl-(1$ ightarrow$6)-$eta$-D-glucopyranoside (6) and kaempferol 3-Ο-$eta$-D-glucuronopyranoside (7)], along with $eta$-sitosterol glucopyranoside (8), were isolated. Compound 1 possessed good activities in all the model systems tested. Compounds 2 and 7 showed scavenging activities in the DPPH and $ONOO^-$ tests, while compounds 3 and 4 were only active in the $ONOO^-$ test. Conversely, compound 8 showed no activities in any of the model systems tested.