Objective To study the humoral immunity stares and distribution pattern of lymphocyte subgroups of peripheral blood mononuclear cell (PBMC) in patients with Kaschin-Beck Disease (KBD), and their relationship with erythrocyte selenium. Methods 23 X-ray diagnosed patients, 22 age-and sex-matched healthy children in KBD affected area (KAA), Aed 25 in KIID non-affected area (KNAA) were randondy selected. Inmonaohistochemistry with monocinnal antibodies anti-CD4, janti CD8. anti-CD20 was conducled to analyze the lymphocyte subsets. Serum IgM, lgA, IgG, Complement C3 and CA were assayed using rate nephalometry (Array 360 System, USA). The contents of erythrocyte selenium was determined by 2,3-diaminonaphthalene fluorescence assay. Results CD4+ and CD8+ eells percentage in PBMCs and serum lgA were significandy lower in KAA than those in KNAA(p<0.05). CD20+ percentage in KAA displayed a decreasittg trend compared to KNAA, although not statiatieally sigmiticanfly. No statistical differences were found in CD4/CD8 ratio, serum loG, lgM, C3 and CA levels. Ewthrncyte selenium level in KAA still showed a pronounced decrease compared to that in KNAA. Correlation analysis showed that erythrocyte selenium contents had a strong association with the CD4 cell percentage (r=0.625, P<0.05), and also a close relationship with serum IgA (r=0.462, P<0.05). In addition, we detected a moderate correlation between the serum lgA mad CIM+ percentage (r=0.130, P>0.05). Conclusion T tken tsgether, out restdts suggested that children in KAA had a comparably low eellulax immmtity level manifested by the marked depression of CD4 and CD8 cells percentage, and their humoral immunity status was also in a state of moderate inunune suppression. Of this immune diller in KBD patients, selenium dalicieney probably played a critical role via affecting the distribution pattern of peripheral blood lymphocyte. Selertlum-deficiency and immune impairment maybe both have something to do with the cause-effect chain of KBD.