AIM: To investigate the effects of Nigella sativa L (NS)and Urtica dioica L (UD) on lipid peroxidation, antioxidant enzyme systems and liver enzymes in CCl4-treated rats.METHODS: Fifty-six healthy male Wistar albino rats were used in this study. The rats were randomly allotted into one of the four experimental groups: A (CCl4-only treated), B (CCl4+UD treated), C (CCl4+NS treated) and D (CCl4+UD+NS treated), each containing 14 animals.All groups received CCl4 (0.8 mL/kg of body weight, sc,twice a week for 60 d). Tn addition, B, C and D groups also received daily J.p. injections of 0.2 mL/kg NS or/and 2 mL/kg UD oils for 60 d. Group A, on the other hand,received only 2 mL/kg normal saline solution for 60 d.Blood samples for the biochemical analysis were taken by cardiac puncture from randomly chosen-seven rats in each treatment group at beginning and on the 60th d of the experiment.RESULTS: The CCl4 treatment for 60 d increased thelipid peroxidation and liver enzymes,and also decreasedthe antioxidant enzyme levels. NS or UD treatment (aloneor combination) for 60 d decreased the elevated lipidperoxidation and liver enzyme levels and also increasedthe reduced antioxidant enzyme levels.The weight ofrats decreased in group A,and increased in groups B, Cand D.CONCLUSION: NS and UD decrease the lipid peroxidation and liver enzymes, and increase the antioxidant defense system activity in the CCl4-treated rats.