The objective of the study is to evaluate the risk of graft failure. The presence of donor specific alloantibodies and the HLA incompatibilities between donor and receptor must be identified. There are several methods to identify alloandibodies that has different sensitivity and different Prognostic Value. Some define a high risk of hyperacute rejection, others an increase in the risk to loss the graft in defined subgroups. First steps of the pretransplant study identify: a) HLA typing of the receptor and available donors; b) alloantibodies by Complement Dependent Cytotoxicity against Panel (PRA-CDC) and screening of alloantibodies against HLA by Solid Phase; c) in sensitized receptors it can be useful to identify acceptable incompatibilities using Single Antigen Solid Phase technique and to evaluate the «Virtual Crossmatch». Pretransplant study (10 days): a) crossmatch by Citotoxicity (CM-CDC) between receptor and donor; b) crossmatch by Flow-Cytometry (FCCM) between receptor and donor specially indicated in the retransplant. Useful also to discard IgM auto-antibodies. Receptors desensitization: the necessity and success probability of desensitization should be evaluated before treatment. Post-Transplant Monitoring: identify alloantibodies for: a) the differential diagnostic of corticorresistant rejection episodes with humoral component, and b) as a marker of long term reduced graft survival probability in the long term. Final remarks: Evaluation should consider the allosensibilization history of the receptor. The cytotoxicity crossmatch indicates a high risk of hyperacute rejection and is considered a contraindication. The Flow Cytometry crossmatch indicates an increase in the probability to loss the graft in the first year that is low for first transplants (>10%) but higher for retransplantation (>30%). The virtual crossmatch by solid phase indicates an increase in the probability to have an antibody mediated rejection (from 5% to 55%) but did not contraindicate always the transplant.