In this overview session, we consider the immunology of clinical kidney transplantation.  We review how our immune system recognizes ABO blood group antigens, major histocompatibility antigens, minor histocompatibility antigens, and non-HLA antigens.  We discuss how our immune system responds to foreign antigen through the innate as well as the adaptive arms of the immune system with its 3 signals.  As well we discuss pre-transplant diagnostic testing and current immunosuppression strategies.  Finally we look at whether outcomes are improving, gaps that need to be addressed to improve patient management and emerging tools that may help us address those areas of need in managing the immune systems of transplant recipients.