To evaluate the correlation between chimerism status and acute graft-versus-host disease (aGVHD) following allogeneic hematopoietic stem cell transplantation. Chimerism of peripheral blood of 124 patients was monitored at regular intervals post-transplant. The chimerism of 124 post-transplant cases of CD3(+)T lymphocytes, 107 cases of CD3(-)CD56(+)CD16(+)NK lymphocytes, 49 cases of CD15(+) granulocytes, and 27 cases of CD19(+)B lymphocytes sorted by fluorescence-activated cell sorter were analyzed by polymerase chain reaction amplification of short tandem repeats. Differences were found in the time between establishment of full donor T-cell chimerism and the occurrence of aGVHD (P = 0.035, two related samples test). Patients with ≥69 % donor chimerism on day +7 in T-cells had higher rates of aGVHD. This study may provide a rational basis for treatment with adoptive immunotherapy at an earlier time, such as day 7 after SCT, than at present to prevent aGVHD.