The hypoglycemic and hypolipidemic effect of continuous intravenous infusion of a lyophilised aqueous extract of the whole plant Ajuga iva (L.) Schreber (Labiatae) (AI-extract) was investigated in anesthetized normal and streptozotocin (STZ)-induced diabetic rats. The AI-extract was administered to a group of rats by continuous intravenous infusion for 4 h at a dose of 4.2 microg/min/100 g body weight; another group was infused with taurine, the reference compound, at the same dose. In normal rats, AI-extract infusion had no effect on plasma glucose or triglycerides, but plasma cholesterol levels were significantly decreased (22%; P<0.05). However, taurine infusion produced significant hypoglycemic, hypocholesterolemic and hypotriglyceridemic effects (all changes, P<0.05). In STZ-diabetic rats, AI-extract infusion reduced plasma levels of glucose by 24 % (P<0.05), cholesterol by 35% (P<0.01) and triglycerides by 13% (P<0.05). Infusion with taurine produced a greater fall in plasma glucose (72%, P<0.01), cholesterol (54%; P<0.001) and triglyceride (24%; P<0.001) levels. Our results indicate that intravenously administered AI-extract exerts hypoglycemic and hypolipidemic effects in diabetic rats by mechanism(s) which appear to be similar to that of taurine, which involve insulin sensitization or an insulin-like effect. The identity and the exact mechanism(s) of action of the active component(s) of the AI-extract are not known. Ajuga iva appears to be a useful plant in the therapy of diabetes, a condition in which hyperglycemia and dyslipidemia coexist quite often.