Hereditary hemochromatosis is a common disorder in people of European origin. The HLA-H gene has been found to have two mutations that apparently cause hemochromatosis. The principal mutation, 845G-->A (C282Y), is believed to have arisen relatively recently in the Celtic population. To determine the incidence of this mutation and the other hemochromatosis-associated mutation, 187C-->G (H63D), among Ashkenazi Jews, a people who are believed to have arrived in Europe in about the 8th Century A.D., we have examined the DNA from 381 unrelated Jewish subjects and 206 non-Jewish white controls. The gene frequency for the 845G-->A mutation among Jewish subjects was only 0.013 compared with a frequency of 0.070 among controls, a difference that is significant at the 0.00001 level. The phenotypically milder nt 187C-->G mutation had a frequency of 0.155 in the non-Jewish population and 0.097 in the Jewish population, a difference that was also statistically significant at the <0.01 level.