Antioxidant activity of hydro alcoholic extract of Nelumbo nucifera seeds (HANN) was studied using in vitro and in vivo models. Total phenolic content in HANN was found to be 7.61 +/- 0.04% (w/w). Characteristic HPTLC fingerprints of HANN were also made using different solvent systems. The HANN exhibited strong free radical scavenging activity as evidenced by the low IC(50) values in both DPPH (1,1-diphenyl-2-picryl hydrazyl) (6.12 +/- 0.41 microg/ml) and nitric oxide (84.86 +/- 3.56 microg/ml) methods. The values were found to be less than those of rutin, the standard used. Acute toxicity of HANN was evaluated in Swiss Albino mice, no signs of toxicity were observed up to the oral dose of 1,000 mg/kg body weight. Administration of HANN to Wistar rats at 100 and 200 mg/kg body weight for 4 days prior to carbon tetrachloride (CCl(4)) treatment caused a significant dose dependent increase (p < 0.05 to p < 0.001) in the level of superoxide dismutase (SOD) and catalase and a significant decrease (p < 0.05 to p < 0.001) in the level of thiobarbituric acid reactive substances (TBARS), when compared to CCl(4) treated control in both liver and kidney. These changes observed at 100 mg/kg body weight treatment were comparable to those observed for standard Vitamin E at 50 mg/kg treatment. Nelumbo nucifera seeds contain alkaloids, saponins, phenolics and carbohydrates. The results support significant antioxidant nature of HANN.