Since ancient times, medicinal plants have been used in various traditional medicinal systems which makes it very important to evaluate the toxicity of such plants. The hepatotoxic Pyrrolizidine alkaloids (PAs) have been considered as an important therapeutic extract that can be obtained from the medicinal plant Ageratum conyzoides. In this regard butanolic extract of the flowers of this plant were evaluated for its toxicity on a panel of normal mouse and human liver cell lines. Firstly, the flowers were extracted in n-Butanol for 24 h and the extract was treated to the normal mouse liver cells; AML 12 cells andthe normal human liver cells THLE-3 cells in an amount dependent manner for 24 h. Both the normal liver cells showed a decrease in cell viability upon increase in the amount of the extract indicating that caution must be exercised while utilizing this plant for medicinal purposes.