Roundup is a glyphosate-based herbicide that includes 78.5% glyphosate and surfactant at lower toxic concentrations. Glyphosate is an organophosphorated non-selective agrochemical widely used in many countries including Turkey and acts after the sprout in a systemic way. The objective of this study was to analyze toxic effects of the herbicide Roundup in rat liver. Animals were treated with 56 mg/kg (p.o.) and 560 mg/kg (p.o.) of Roundup (78% glyphosate + surfactant) each day, during 5 and 13 weeks. Hepatotoxicity was monitored by quantitative analysis of the serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) activities and measured amount of serum lipoprotein (LDL, HDL), total cholesterol and creatinine were used as the biochemical markers of liver damages. Besides the biochemical analysis, we also investigated liver tissues histopathologically. Sub-chronic treatment, starting from the low and high doses of Roundup, it was observed that there were mild effects on activity of ALT, AST and LDH enzymes indicating the hepatic toxicity induced by Roundup. It was found that the mild effects were different on the enzymes in male and female rats of treatment groups. Also it was found some difference in serum lipoprotein (LDL, HDL) and t-cholesterol. There was no difference creatinine value between control and treatment groups but it was observed that degenerative formation such as mononuclear cell infiltration and congestion of the liver tissues of treatment groups. (c) 2007 Published by Elsevier B.V.