Antioxidant activity and hepatoprotective potential of Phyllanthus niruri, a widely used medicinal plant, were investigated. Methanolic and aqueous extract of leaves and fruits of P. niruri showed inhibition of membrane lipid peroxidation (LPO), scavenging of 1,1-diphenyl-2picrylhydrazyl (DPPH) radical and inhibition of reactive oxygen species (ROS) in vitro. Antioxidant activity of the extracts were also demonstrable in vivo by the inhibition of the carbon tetrachloride (CCl4) - induced formation of lipid peroxides in the liver of rats by pretreatment with the extracts. CCl4 - induced hepatotoxicity in rats, as judged by the raised serum enzymes, glutamate oxaloacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT), was prevented by pretreatment with the extracts, demonstrating the hepatoprotective action of P. niruri.