Picroliv, an iridoid glycoside mixture prepared from the roots and rhizomes of Picrorhiza kurroa was found to be an effective inhibitor of hepatocarcinogenesis induced by N-Nitrosodiethylamine (NDEA) in rats. Animals administered with NDEA had large hepatic nodules and the liver weight was increased to 6.17 +/- 1.0 g/100 g.b.wt. as compared to the normal liver weight 2.84 +/- 0.08 g/100 g.b.wt. Picroliv administration (200 mg/Kg.b.wt) reduced the liver weight to 3.30 +/- 0.23 g/100 g.b.wt. Oral administration of Picroliv reduced NDEA-induced elevation of gamma-glutamyltranspeptidase (gamma-GT) in serum and liver to that of normal rats. Moreover, elevated levels of bilirubin, alkaline phosphatase (ALP), glutamatepyruvate transaminase (GPT) and serum peroxides were also found to be significantly reduced by Picroliv administration. Similar observations were noticed in glutathione (GSH) and glutathione S-transferase (GST) levels. Histopathological analysis of the Picroliv treated rat liver resembles that of a normal liver except for a few alterations such as hepatocytomegalia and karyomegalia in some focii. The results are indicative of the chemopreventive potential of Picroliv against chemically-induced liver tumours.