To observe the roles of recipient-derived cells in renal allografts with acute cellular rejection (ACR), eight male patients who had received a female donor kidney were enrolled, with protocol renal allograft biopsies. Three of them suffered from ACR, and the other five with normal function. Biopsy sections were detected for the presence of recipient-derived cells and their phenotypes. Recipient-derived cells appeared in the tubular epithelium as early as 13 days posttransplant, with the phenotype of cytokeratin(+)/CD45(-). They also localized in the medium walls of arterioles and expressed alpha-SMA. In patients with ACR, recipient-derived tubular cells increased persistently during the first 6 months (3.8 to 6.6%). Long-term follow up showed a decline in their number when ACR ameliorated. In patients without ACR, the infiltration rate remained stable (0.6-2.3%). Recipient-derived cells participate the remodeling of renal allografts. They might have a close relationship with ACR outcome and with vascular structure remodeling.