In this study the known promoter region of P450aldo gene (CYP11B2) was investigated in patients with idiopathic hyperaldosteronism, a disease characterised by hypertension due to aldosterone oversecretion. We amplified the 2.2 kb promoter region of 6 patients and 7 controls from the same ethnic population by PCR and sequenced the product. Thirteen polymorphic sites were found. Of the most significant, one was within a predicted CRE and another previously described polymorphic site was located in a putative SF-1 binding site. To elucidate the allelic distribution of the polymorphisms, the PCR products were cloned and both alleles for each patient were sequenced. As the same alleles and allele combinations were found in hypertensive patients as well as in normal subjects, it was concluded that none of the polymorphisms was responsible for hyperaldosteronism.