The effect of aqueous extract from the roots of Rumex patientia L. (Polygonaceae) (D-1), a traditional Turkish medicine used as a laxative and cholagogue, on drug-metabolizing enzymes, such as cytochrome P4502E1, NADPH cytochrome c reductase, NADH cytochrome b5 reductase and glutathione-S-transferase (GST); and serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were studied in male Wistar albino rat liver. A significant increase was observed in cytochrome P4502E1 and GST activities, but not in NADPH-cytochrome c reductase and NADH-cytochrome b5 reductase activities. Serum AST and ALT activities were found within the normal laboratory range values. The results demonstrated that the aqueous extract of R. patientia triggers induction of cytochrome P4502E1 in liver and cytosolic GST activity.