Objective:To evaluate the in vivo trypanocidal activity of the methanol extract and fractions of Abrus precatorius seeds in mice.Methods:Parasiteamia was induced unto mice by intraperitoneal injection of 1.25×10~5 Trypanosoma in normal saline.Five days when a high level of parasiteamia was established treatment commenced until ten days.The mice were treated with 10,20 and 40 mg/kg bt.of the extract and 5 and 10 mg/kg bt.of the fraction(F_2),respectively for 5 days.Diminazene acelurate at the dose of 3.5 mg/kg bt.for two days was used as the reference drug.The level of parasitaemia and packed cell volume(PCV) of the animals estimated. Results:At doses of 10,20 and 40 mg/kg the crude extract showed a sharp reduction in the level of parasitaemia in mice compared with the untreated group.The mice treated with F,at doses of 5 and 10 mg/kg showed a sharp reduction in the level of parasitamia to zero in day 9,and a gradual recovery from the 12th day of treatment.This effect is comparable to that of the mice treated with 7 mg/kg of standard drug diminazene aceturate.The PCV of the treated showed a gradual decrease with time,but not as much as the untreated group.Phytochemical screening revealed the presence of glycosides,alkaloids,carbohydrates,tannins and proteins in the Abrus precatorius powder while F_2 was rich in alkaloids.Conclusions:This study shows that both the extract and the fractions of Abrus precatorius seeds exhibited a promising trypanocidal property.Alkaloids may be responsible for the observed activity. Objective: To evaluate the in vivo trypanocidal activity of the methanol extract and fractions of Abrus precatorius seeds in mice. Methods: Parasiteamia was induced to mice by intraperitoneal injection of 1.25 × 10 ~ 5 Trypanosoma in normal saline. Fever days when a high level of parasiteamia was established treatment commenced until ten days. The mice were treated with 10,20 and 40 mg / kg bt. of the extract and 5 and 10 mg / kg bt. of the fraction (F_2), respectively for 5 days. Diminazene acelurate at the dose of 3.5 mg / kg bt.for two days was used as the reference drug. The level of parasitaemia and packed cell volume (PCV) of the animals estimated. Results: At doses of 10, 20 and 40 mg / kg the crude extract showed a sharp reduction in the level of parasitaemia in mice compared with the untreated group. The mice treated with F, at doses of 5 and 10 mg / kg showed a sharp reduction in the level of parasitamia to zero in day 9, and a gradual recovery from the 12th day of treatment. This effect is comparable to that of the mice treated with 7 mg / kg of standard drug diminazene aceturate. PCV of the treated showed a gradual decrease with time, but not as much as the untreated group. Phytochemical screening revealed the presence of glycosides, alkaloids, carbohydrates, tannins and proteins in the Abrus precatorius powder while F_2 was rich in alkaloids. Conclusions: This study shows that both the extract and the fractions of Abrus precatorius seeds exhibited a promising trypanocidal property. Alkaloids may be responsible for the observed activity.