Hepatoprotective effect of andrographolide (the major active diterpenoid lactone of the plant Andrographis paniculata) was studied on acute hepatitis induced in rats by single dose of galactosamine (800 mg/kg, ip)/paracetamol (3g/kg, po). Hepatoprotective activity was monitored by estimating the serum transaminases (GOT and GPT), alkaline phosphatase and bilirubin in serum, hepatic triglycerides, and by histopathological changes in the livers of experimental rats. Pre-treatment and/or post-treatment of rats at different time intervals with different doses of andrographolide in the two experimental models of hepatotoxicity showed that treatment of rats with 400 mg/kg, ip or 800 mg/kg, po, 48, 24 and 2 h before galactosamine administration or with 200 mg/kg, ip, 1, 4 and 7 h after paracetamol challenge leads to complete normalisation of toxin-induced increase in the levels of all the five biochemical parameters, and significantly ameliorates toxin-induced histopathological changes in the livers of experimental rats. The results confirmed the in vivo hepatoprotective effect of andrographolide against galactosamine or paracetamol-induced hepatotoxicity in rats. Since the protective effect of andrographolide was observed in two types of intoxication, which are very different in their primary mechanism of inducing hepatotoxicity, it is suggested that protective mechanisms of andrographolide which are not specific to galactosamine or paracetamol toxicity may be responsible for the hepatoprotective activity of the compound.