目的　通过研究中国汉族人群δ氨基 γ 酮戊酸脱水酶 (ALAD)基因型 ,探讨中国儿童是否存在ALAD基因的遗传多态性及其频率分布特点 ,以确定遗传因素对儿童血铅水平的影响。方法　整群抽取对铅毒性较为敏感的 6～ 10岁儿童 2 2 9名为研究对象。通过PCR及限制性内切酶酶切分析两种ALAD等位基因的频率。结果　所研究儿童中ALAD 1 1型有 2 11例 ,ALAD 1 2型有 18例。ALAD2 基因频率为 8% ;ALAD1基因频率为92 %。未发现ALAD 2 2型。结论　中国人ALAD基因存在遗传多态性 ;从遗传特质上来说 ,中国儿童对铅毒性的易感性可能低于欧美儿童。 Objective To investigate the genetic polymorphism of ALAD gene and its frequency distribution in Chinese children by studying the genotype of δ-aminolevulinic acid dehydratase (ALAD) in Chinese Han population to determine the effect of genetic factors on blood lead levels in children. Methods A total of 299 children aged 6 to 10 who were sensitive to lead toxicity were enrolled in this study. The frequencies of the two ALAD alleles were analyzed by PCR and restriction endonuclease digestion. Results There were 2,11 ALAD type 1 and 18 ALAD type 1 in children studied. ALAD2 gene frequency was 8%; ALAD1 gene frequency was 92%. No ALAD type 2 2 was found. Conclusion The genetic polymorphism of Chinese ALAD gene exists. From genetic characteristics, the susceptibility of Chinese children to lead toxicity may be lower than that of European and American children.