The enzyme 11 beta-hydroxysteroid dehydrogenase type 2 (11BHSD2) converts cortisol to cortisone in the kidney, thereby protecting the mineralocorticoid receptor from the mineralocorticoid actions of cortisol. The syndrome of Apparent Mineralocorticoid Excess (AME), a rare monogenic form of early onset hypertension with autosomal recessive inheritance, is caused by homozygous or compound heterozygous loss of function mutations in the 11BHSD2 gene. Association has been reported between a microsatellite marker flanking the 11BHSD2 gene (D16S496) and primary hypertension. The aim of this study was to identify variants in the 11BHSD2 gene and to test if such variants or the D16S496 are associated with primary hypertension, in Swedes. To address this, the coding sequences of the 11BHSD2 gene was screened for mutations in 20 patients with primary hypertension with single strand conformation polymorphism and direct DNA sequencing techniques. A polymorphism was identified in exon 3; G534A (Glu178Glu). This polymorphism and the D16S496 microsatellite were tested for association with primary hypertension in a population consisting of 292 patients with primary hypertension and 263 normotensive control subjects. The frequency of G534G homozygotes was higher in patients with primary hypertension than in normotensive control subjects (92.8% vs 87.8%; P < 0.05). The allele frequencies of the D16S496 microsatellite did not differ between the two groups (chi(2) = 11.0, df = 10; P = 0.36). In conclusion, over-representation of individuals homozygous for the G534 allele in hypertensive patients compared with control subjects suggests that a mutation in linkage disequilibrium with the G534A polymorphism could increase susceptibility to primary hypertension. Journal of Human Hypertension (2000) 14, 819-823