Acquired aplastic anemia (AA) is an immune mediated bone marrow failure syndrome which is associated with impaired T-cell immune responses. In this work we investigated the role of Th17 immune response in AA. Our results showed that the absolute numbers of circulating IL-17-producing CD4(+) T cells and CD4(+)CD161(+)CCR6(+) cells, the blood plasma level of IL-17, and the expression level of Th17 lineage-specifying transcription factor RORC in circulating CD4(+) T cells, were not increased in AA. These results suggest that Th17 immune response may not play an important role in the pathogenesis of AA.