Abstract: ［Abstract］Objective　To investigate the prevalence and the phenotype of Helicobacter pylori（Hp） infection and the human leukocyte antigen（HLA）-DR expression in the peripheral blood lymphocytes and monocytes in family members of children with recurrent abdominal pain，and to explore the association between HLA-DR expression and Hp-associated recurrent abdominal pain．Methods　Venous blood specimen was obtained from 57 family members of 13 children with recurrent abdominal pain and 37 adult volunteers for HLA-DR expression on monocytes by flow cytometry and for the Hp type by Hp immunophenotyping method．Individuals were divided into children with recurrent abdominal pain， adult family members with recurrent abdominal pain and the normal control group according to symptoms．The phenotype of Hp infection and the human leukocyte antigen （HLA）-DR expression in the peripheral blood lymphocytes and monocytes were analyzed and compared among the three groups．Results　The positive rate of Hp immunophenotyping antibody test in 94 individuals was 67.0%， and the percent of HpⅠtype was 80.95% while HpⅡtype was 19.05%. The positive rate of Hp in 57 family members of children with recurrent abdominal pain was 94.7%，and the percent of HpⅠtype was 77.8% while HpⅡtype was 22.2%．Hp immunophenotype was similar in the same family. Hp infection had the family cluster and line phenomenon．The expression of HLA-DR in peripheral blood monocytes among three groups had difference （H＝10.624，P＜0.05），children and family members with recurrent abdominal pain expressed higher than those without recurrent abdominal pain，but the result had no difference in lymphocytes（H＝0.966，P＞0.617）．Conclusions　 The seropositive rate of Hp antibodies is high in the family members with recurrent abdominal pain. There is the familial cluster and line phenomenon in the family members with recurrent abdominal pain by Hp infection. The higher expression of HLA-DR on monocytes in familial members with recurrent abdominal pain caused by Hp infection may be associated with active immunological function stimulated by Hp chronic infection.