Glucocorticoid-suppressible hyperaldosteronism (GSH) is an uncommon form of dominantly inherited hypertension caused by the inheritence of a chimaeric 11 beta-hydroxylase/aldosterone synthase gene. Affected individuals appear to have an increased risk of premature morbidity and mortality from stroke, but treatment with low doses of dexamethasone can completely reverse the biochemical and clinical features. We assessed the clinical and genetic features of 5 British kindreds with GSH, the largest collection outwith the United States, and determined the location of the crossover regions in the chimaeric gene of all 5 kindreds. All of the kindreds were of celtic origin, another feature peculiar to GSH. In total 19 out of 60 individuals screened by genotyping were found to possess the chimaeric gene and sequencing of the chimaeric gene revealed that all the crossover regions were within the exon 3- exon 4 region of, in keeping with previous studies, and three kindreds possessed indistinguishable chimaeric genes.