Much attention has been paid to only natural antibody titer of the recipients in ABO-incompatible kidney transplantation. In this study, we looked at the distribution of blood type antigens in the kidney tissue. Thirty-seven biopsy specimens from patients with nephritis or transplanted kidneys were recruited. Fifteen were type A, 14 were type B, and 8 were type AB. Kidney tissues were stained with anti-A or anti-B antibody using immunohistological staining. The stained dots in each section were regarded as the area and were measured by image analyzer. B antigen was expressed very weakly both in the glomeruli and in interstitium as compared with A antigen. In type AB, B antigen was less expressed than A antigen. Based on these results, we performed B-incompatible kidney transplantation. No rejection was seen without preoperative depletion of natural antibody and splenectomy. These results may suggest that type B-incompatible kidney transplantation might possibly be performed without preoperative depletion of natural antibodies.