Abstract: A single base-pair polymorphism involving a mutation from Guanine (G), in individuals unaffected by the hereditary hemochromatosis (HH) gene defect, to Adeninc (A), in individuals affected by the HH gene defect is disclosed. The presence or absence of the polymorphic allele is highly predictive of whether an individual is at risk from HH: the polymorphism is present in 82% of affected individuals and only 4% of a random population screen. Methods of diagnosis, markers, and primers are disclosed and claimed in accordance with the present invention.