Objective:To investigate the impact of the endogamous marriage culture on the prevalence of the hemoglobin E(HbE) recessive variant.Methods:The prevalence of the hemoglobin E(HbE)recessive variant was determined by dot-blot hybridization in 4 endogamous villages(1 Mlabri and 3 Htin ethnic groups) in comparison with 9 other nearby non-endogamous populations.Results:Although the overall HbE prevalence in the population studied(8.44%,33/391)was not significantly different from that of the general southeast Asian population,a high prevalence and individuals with homozygous HbE were observed in two villages,the Mlabri from Wiang Sa district and the Htin from Thung Chang district of Nan province(26.3%and26.9%,respectively).The low HbE allelic frequency noticed in some endogamous populations suggests that not only endogamy but also other evolutionary forces,such as founder effect and HbE/β-thalassemia negative selection may have an effect on the distribution of the HbE trait.Conclusion:Our study strongly documents that cultural impact has to be considered in the extensive prevalence studies for genetic disorders in the ethnic groups of northern Thailand. Objective: To investigate the impact of the endogamous marriage culture on the prevalence of hemoglobin E (HbE) recessive variant. Methods: The prevalence of the hemoglobin E (HbE) recessive variant was determined by dot-blot hybridization in 4 endogamous villages (1 Mabri and 3 Htin ethnic groups) in comparison with 9 other nearby non-endogamous populations. Results: Although the overall HbE prevalence in the population studied (8.44%, 33/391) was not significantly different from that of the general southeast Asian population, a high prevalence and individuals with homozygous HbE were observed in two villages, the Mlabri from Wiang Sa district and the Htin from Thung Chang district of Nan province (26.3% and26.9%, respectively). The low HbE allelic frequency noticed in some endogamous populations suggests that not only endogamy but also other evolutionary forces, such as founder effect and HbE / β-thalassemia negative selection may have an effect on the distribution of the HbE trait. Confclusion: Our s tudy strongly documents that cultural impact has to be considered in the extensive prevalence studies for genetic disorders in the ethnic groups of northern Thailand.