In the present study, we investigated the inhibitory natural killer cell receptor (NKR) expression of CD94/NKG2A on PBMC after allogeneic bone marrow transplantation (BMT). The proportion of CD94 expression on PBMC was higher in patients without chronic graft-versus-host disease (cGVHD) and also in cGVHD patients with good response to conventional immunosuppressive therapy than in cGVHD patients with poor response. Also, the proportions of CD94+/CD3+ cells and CD94+/CD8+ cells were higher in cGVHD patients showing good response. In addition, the proportion of NKG2A-expressing cells was higher in patients without cGVHD than in patients with cGVHD. Therefore, chronic allostimulation after allo-BMT may augment the proportion of CD94/NKG2A-positive cells, and these cells may play some role in the regulation of alloresponse in some patients.