Objectives: To evaluate the presence of HLA class I and class II antibodies in patients on the waiting list for kidney transplant exhibiting reactivity against a panel of histocompatibility antigens. Material and methods: This retrospective study was performed from May 2015 to May 2016 using the database of 4,195 chronic renal disease patients available at the HLA Laboratory of the Blood Center Foundation of Ribeirão Preto. Levels of HLA antibodies were determined by mean fluorescence intensity (MFI) and crossmatches were performed using a complement-dependent cytotoxicity (CDC) assay. Results: At the time of the study, 614 patients exhibiting positive crossmatch presented specific antibodies against putative donor antigens (DSA- Donor Specific Antibody), among them 352 had DSA for HLA-A, 431 for HLA-B and 167 for HLA-DR. The other HLA loci did not obtain DSA minimum values. The screened MFI values for selecting patients for transplantation ranged from 1,500 to 20,000, and the average were 8,007 for HLA-A, 8,308 for HLA-B, and 8,289 for HLA-DR. When stratifying the MFI values, we observed for all loci that MFIs> 10,000 were more frequent for HLA-A (36%), HLA-B (40%) and HLA-DR (33%). Mapping the frequencies of the allele groups, we observed that A2, B15 and DR13 were the most frequent ones, whereas A33, B41, DR12 and DR-9 appeared less frequently. Noteworthy, A23 had the highest mean MFI (11,717) and the lowest MFI was A34 (5,302). The most frequent A2 allele group had MFI 8,113. B41 had the highest mean of MFI (14,267) and the lowest MFI was B45 (2,775). On the other hand, DR9 had the highest mean MFI (14,202) and DR12 the lowest (1,544). The most frequent B15 allele group had an average MFI of 9,057 and DR13 an MFI of 11,453. Discussion: The presence of DSA has high clinical relevance, since the presence of anti-HLA antibodies in post-transplant patients has been strongly associated with antibody-mediated rejection, accelerated acute rejection and with loss of graft. Patient follow-up is performed for each DSA, evaluating its MFI at various post-transplant periods to reduce the likelihood of any type of rejection. The most used MFI cutoff point for selecting patients for transplantation is 1,500; however, we observed that the lowest positive MFI values were 5,302 for HLA-A, 2,775 for HLA-B and 1,544 for HLA-DR-, indicating remarkable differences according to the HLA- loci. Another interesting fact was that although some alleles appear more frequently in patients, they were not always the ones that reacted with greater intensity. Conclusion: We reported that the levels of MFI≥5,000 is well-correlated with the results of CDC crossmatching for the HLA-A locus, whereas an MFI≥1,500 is observed for the HLA-B and HLA-DR loci. Notwithstanding, it is worth mentioning that the pre-transplant MFI values are not the sole predictors for transplant outcome, since several other factors may interfere on the rejection process.