A missense mutation (Gly40Ser) in exon 2 of the glucagon receptor gene (GCG-R) was shown to reduce ligand affinity and impair cAMP response. We conducted a case-control study with a sample of 741 French hypertensive patients with moderate to severe hypertension and 412 normotensive control subjects, who were genotyped for this biallelic variant by use of hybridization with allele-specific oligonucleotides. The Gly40Ser polymorphism was not significantly associated with hypertension in the whole study population, although the frequency of 40Ser carriers in hypertensive subjects was double that in normotensive subjects (3.1% in hypertensives versus 1.5%; P=0.087). However, the separate analysis of both genders revealed that 40Ser allele carriers were significantly more frequent (P=0. 035) among male patients (17/429; 4.0%) than among normotensive male controls (2/242; 0.8%), whereas no significant difference was observed in female subjects (6/312 in hypertensives and 4/170 in normotensives). Further studies are required to interpret the significance of this association.