Hypoglycaemic, antihyperglycaemic and hypolipidemic activities of the aqueous and 50% ethanolic extracts of Caesalpinia bonducella Fleming (Leguminosae) seeds were studied in normal and streptozotocin (SZ)-diabetic rats. In normal rats, both the extracts exhibited hypoglycaemic activity as early as 4 h after administration at a lower dose of 100 mg/kg. The hypoglycaemia produced by the aqueous extract was of prolonged duration as compared to ethanolic extract. In diabetic rats, both the extracts produced significant (P < 0.01) antihyperglycaemic effect from day 5 onwards. Aqueous extract also exhibited antihypercholesterolemic and antihypertriglyceridemic effects in SZ-diabetic rats. These results suggest that C. bonducella seeds possess an antidiabetic principle and can be useful for treatment of diabetes. Further studies are warranted to fractionate the active principle and to find out its exact mechanism of action.