RANTES (regulated upon activation, normal T cell expressed and secreted) is a chemotactic cytokine (a chemokine) for memory T lymphocytes, monocytes, and eosinophils. RANTES expression was studied in renal allograft biopsy specimens. Although RANTES was not expressed in samples taken one hour after transplantation, or in native renal biopsy specimens from patients with cyclosporin nephrotoxicity, it was expressed during cell-mediated transplant rejection. RANTES mRNA was detected in infiltrating mononuclear cells and renal tubular epithelium, and RANTES protein was localised to mononuclear cells, tubular epithelium, and vascular endothelium. This suggests RANTES has a role in allograft rejection.