As a major counterregulatory hormone of insulin, glucagon plays an important role in regulating glucose homeostasis through its binding to the glucagon receptor. Recently a missense mutation in the glucagon-receptor gene (Gly40Ser) was found to be associated with type 2 diabetes in France and Sardinia, with a frequency as high as 4.6% and 8.3%, respectively. This mutation was also found to be associated with essential hypertension in the white population with a frequency of 5.4%. To investigate the role of this mutation in the pathogenesis of type 2 diabetes and essential hypertension in Taiwanese population, we screened 121 normal controls, 213 unrelated subjects with type 2 diabetes, and 107 unrelated subjects with essential hypertension by use of polymerase chain reaction/restriction fragment length polymorphism (PCR-RFLP). None of the Taiwanese subjects recruited in the study had this receptor mutation. Our results demonstrate a strong genetic heterogeneity among the ethnic group and suggest that the Gly40Ser mutation of the glucagon receptor gene plays little role, if any, in the pathogenesis of type 2 diabetes and essential hypertension in the Taiwanese population.