Antineoplaston A2, 25 mg/ml, was administered to mice in the form of daily intraperitoneal injections for 270 days. The mice were further observed up to 365 days. The total number of mice included in the experiment was 160, both sexes being represented equally. The animals were divided into four groups, each group containing 20 males and 20 females. The first group received 107 mg/kg body weight per day of Antineoplaston A2, the second 646 mg/kg and the third one 1300 mg/kg daily. The fourth group was kept as the control. Two male and two female mice were sacrificed on days 30, 60, 90, 180 and 365 and underwent complete physical, gross pathological and microscopic examination. No toxic effects were observed. In conclusion, daily intraperitoneal injections of Antineoplaston A2 to mice at the dosage level of 107 mg/kg, 646 mg/kg and 1300 mg/kg for 270 days did not produce any toxic effect.