In oral glucose tolerance tests with methanolic extract of non-boiled and boiled Lathyrus sativus seeds, both the extract significantly and dose-dependently reduced blood glucose concentrations in glucose-loaded mice. At extract doses of 100, 200 and 400 mg/kg of non-boiled seeds (MELSNB), the reductions in blood glucose levels were, respectively, 37.7, 44.8, and 48.8%. The percent reductions in blood glucose levels with methanolic extract of boiled seeds (MELSB) were, respectively, 31.0, 45.6, and 47.3%. In comparison, a standard antihyperglycemic drug, glibenclamide, when administered at a dose of 10 mg per kg, reduced blood glucose level by 48.0%. The results suggest that seeds of Lathyrus sativus can serve as an effective antihyperglycemic agent and so can prove beneficial for diabetic patients with high blood glucose levels.