This study was designed to investigate the effects Nigella sativa L. (NS) and Urtica dioica L. (UD) on lipid peroxidation, antioxidant enzyme systems and some liver enzymes in carbon tetrachloride (CCl4)-treated rats. A total of 60 healthy male Sprague-Dawley rats were utilized in this study. The rats were randomly allotted into one of four experimental groups: A (CCl4 -only treated), B (CCl4 + UD treated), C (CCl4 + NS treated) and D (CCl4 + UD + NS treated), each containing 15 animals. All groups received CCl4 [0.8 ml/kg of body weight, subcutaneously, twice a week for 90 days starting day 1]. In addition, B, C and D groups also received daily intraperitoneal injections of 0.2 ml/kg NS or/and 2 ml/kg UD oils for 45 days starting day 46. Group A, on the other hand, received only 2 ml/kg normal saline solution for 45 days starting day 46. Blood samples for the biochemical analysis were taken by cardiac puncture from five randomly chosen rats in each treatment group at beginning, at 45th and at 90th day of the experiment. The CCl4 treatment for 45 days increased the lipid peroxidation and liver enzymes, and also decreased the antioxidant enzyme levels. NS or UD treatments (alone or combination) for 45 days starting day 46 decreased the elevated lipid peroxidation and liver enzyme levels and also increased the reduced antioxidant enzyme levels. Live weights of the rats decreased in group A, and increased in groups B, C and D. It is concluded that NS and UD decrease the lipid peroxidation and liver enzymes, and increase the antioxidant defence system activity in the CCl4-treated rats.