Abstract: The current study was designed to determine whether dietary grapeseed oil inhibits liver cytotoxicity induced by 7,12- dimethylbenz(a)anthracene (DMBA) in the frog, Rana ridibunda. The experimental animals were divided into five groups and treated for 2 weeks with 7,12- dimethylbenz(a)anthracene, DMBA plus grapeseed oil, grapeseed oil, olive oil and last group was untreated and used as control. Liver enzymes, lactate dehydrogenase, glutamic oxaloacetic acid transaminase, glutamic pyruvic acid transaminase and alkaline phosphatase were chosen to assess liver function. In comparison with control, the administration of DMBA alone significantly elevated the activity of liver lactate dehydrogenase, while the activities of glutamic oxaloacetic acid transaminase, glutamic pyruvic acid transaminase and alkaline phosphatase were declined. Similar results were noted in frogs treated with DMBA plus grapeseed oil. Moreover, it is found that the changes were more pronounced in frogs treated with DMBA plus grapeseed oil than those treated with DMBA. The activities of these enzymes in frogs exposed to grapeseed oil or olive oil were not significantly different from those of controls. These results indicate that grapeseed oil effectively increases DMBA-induced hepatotoxicity in the frogs. Also, the results suggested that grapeseed oil has enhancing effects of DMBA metabolic activation.