The antioxidant potential of Argyreia argentea methanol stem extract was evaluated by 2,2-diphenyl-1-picrylhydrazyl free radical scavenging method. The extract showed very significant effect as antioxidant in comparison to ascorbic acid, a reference antioxidant. The radical scavenging activity showed by the extract was a dose dependent phenomenon. The extract at the concentration of 400 μg/ml among five different concentrations ( 10, 50, 100, 200, 400 μg/ml ) showed the highest scavenging activity, 94.86%. The stem extract was also evaluated for its cytotoxic properties by measuring significant LC50 value in a Brine-Shrimp lethality bioassay . LC50 value of Argyreia argentea stem extract was found 939.18 μg/ml, at a 95% confidence limit, giving the lower and upper limits 608.98 and 2043.9 μg/ml, respectively. Keywords : Argyreia argentea; DPPH; Ascorbic acid; Scavenging activity; Gallic acid. © 2010 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. DOI: 10.3329/jsr.v2i3.4772 J. Sci. Res. 2 (3), 523-530 (2010)