Objective：To study the change of immunological response and cell proliferation in breast tissues augmented by polyacrylamide hydrogel injection(PHI).Methods:The expression of CD68,CD25 and PCNA in 20 breast tissues with indurations,12 without indurations after breast augmentation by PHI,and 10 normal breast tissues was examined by immunohistochemistry P-V6000; analysis was also done by H-E staining.Results:Hyperplasia of fibrous tissue and infiltration of inflammatory cells and macrophages were found in the breast and adjacent tissues 3-8 years after PHI.Positive cells of CD68 ,CD25 and PCNA hardly existed in the normal tissues,but the breast tissues around the polyacrylamide hydrogel had many positive cells of CD68 and PCNA,especially in cases with indurations;there were significant differences between the 3 groups(P<0.01); and the numbers of cells positive of CD25 were similar between the 3 groups.Conclusion:Long-term implantation of polyacrylamide hydrogel can cause immunological reaction and cell proliferation in the local adjacent tissues.