We present a case report of a 30-year-old man, who hyperacutely rejected a blood group identical, HLA-haploidentical living related kidney graft in spite of the fact that he had never been immunized. Anti-endothelial IgG antibodies that did not react with monocytes were detected with flow cytometry, on a panel of human umbilical cord cells in his serum retrospectively. On the basis of this experience we put for consideration the possibility of regular examination of non-HLA antibodies in potential living graft recipients.