Chronic renal failure patients need regular blood transfusion support to treat anemia and the development of erythrocyte alloantibodies complicates transfusion therapy. The aim of this study was to determine the frequency and specificity of alloantibodies against red cell antigens in CRF patients. This was a descriptive crosssectional study done in the blood bank, Port Sudan, during the period of May-September 2012. A total of 84 patients (58 male and 26 female) with CRF who received at least one unit of RBC matched for ABO & Rh(D) antigens only were enrolled. Sera were screened for the presence of alloantibody by antibody screening test. The positive samples were subjected for antibody identification. The incidence of alloantibody among CRF patients was 13.1 % and the most common alloantibodies were Anti-c (27.3 %), anti-C (18.2 %), and anti-K (18.2 %). The risk of alloimmunization among CRF patients was 4.8 % with the frequency of 13.1 % and Anti-c being the commonest alloantibodies identified.