Objective: To assess geographic differences in the frequencies of HFE C282Y and H63D genotypes in six racial/ethnic groups recruited in the Hemochromatosis and Iron Overload Screening (HEIRS) Study. Design: HFE C282Y and H63D genotypes of 97,551 participants, ages ≥25 years, who reported that they belonged to one of six racial/ethnic groups, were analyzed. HFE genotype frequencies were compared among the racial/ethnic groups and among the HEIRS Study field centers within each racial/ethnic group. Results: The distribution of HFE C282Y and H63D genotypes differed among racial/ethnic groups (P<.0001) and among field centers in Hispanics, Asians, Whites, and Blacks (each P<.05). Genotype frequencies were similar among field centers in Native Americans and Pacific Islanders. Frequencies of C282Y and H63D genotypes were greatest in Whites. The lowest frequencies of C282Y genotypes were observed in Asians; Blacks had the lowest H63D genotype frequencies and the highest frequency of the wild-type genotype. Among racial/ethnic groups, Hispanics had the greatest variation in HFE genotypes across geographic regions. Conclusion: HFE C282Y and H63D genotype frequencies vary significantly between racial/ethnic groups and within some racial/ethnic groups across geographic regions.