The aqueous leaf extract of Vernonia amygdalinu, Del, (Compositae) given i.p. produced a dose-related fall in blood sugar. A dose of 80 mg/kg body weight of adult rabbit produced a maximum lowering of blood sugar in both fasted normal and alloxanized rabbits. The fasting blood sugar in normoglycaemic rabbits w-as reduced from 96 mg% to 48 mg% in 4 h. In alloxanized rabbits, the blood sugar was reduced from the mean value of 520 mg% to 300 mg% in 8 h. The hypoglycaemic effects were compared with those of tolbutamide. Acute toxicity studies of the extract in mice gave LDso value of 1122mg/kg body weight when given i.p. The blood sugar lowering effect of Vernonia amygdalina extract may involve a mechanism not related to insulin secretion.