The effects of 4 weeks oral intake of Nigella sativa L. (NS) oil on some liver function tests and D-galactosamine- or carbon tetrachloride-induced hepatotoxicity were investigated in male albino rats. In another series of experiments, the effect of the oil on serum lipid profile was examined in male spontaneously hypertensive rats of stroke prone strain and Wistar Kyoto rats. The study showed that daily administration of the oil per se (800 mg/kg orally for 4 weeks) did not adversely effect the serum transaminases (ALT and AST), alkaline phosphatase, serum bilirubin or prothrombin activity in normal albino rats. When the oil was given for 4 weeks prior to induction of hepatotoxicity by D-galactosamine or carbon tetrachloride, it was able to give complete protection against d-galactosamine and partial protection against carbon tetrachloride hepatotoxicity. NS oil showed a favourable effect on the serum lipid pattern where the administration of the oil (800 mg/kg orally for 4 weeks) caused a significant decrease in serum total cholesterol, low density lipoprotein, triglycerides and a significant elevation of serum high density lipoprotein level.