In the field of organ transplantation, donor-specific anti-HLA antibodies (DSA) have gained more popularity, as antibody-mediated rejection (AMR) has been recognized as an important factor to determine allograft survival. Thus, it is reasonable to believe that appropriate control of DSA is directly linked to well-managed immunosuppression, resulting in free from AMR. First, in order to prevent and manage AMR, it is of vital importance to be familiar with updated knowledge regarding crossmatch test and DSA detection methods, including intra-graft DSA. Second, it is also crucial to understand the standard criteria to diagnose AMR. Although pathological diagnosis and serum DSA (s-DSA) detection play the central role, the recent trend seems to be detection of intra-graft DSA (g-DSA). Third, regarding organ transplantation between sensitized pairs, the acceptable outcomes are obtained owing to recent preoperative desensitization protocols: depletion/modification of B cells, apheresis for antibodies, and inhibition of reaction between DSA and HLA. Finally, we would like to discuss the treatment of AMR. Further advances in diagnosis methods and emergences of effective treatments would be expected for acceptable control of AMR. In this chapter, we will review from the basics to recent topics in order to understand DSA and AMR.