Several factors might have contributed to the high alloimmunization and autoimmunization rate observed in this study, including the heterogeneity of the population living in Kuwait, lack of better-matched donors for those patients, and the use of poststorage leukodepleted blood. It is recommended that thalassemia patients receive blood matched for Rh and Kell antigens and prestorage leukodepleted RBCs.

<i>Objective:</i> The aim of this study was to analyze the alloimmunization against red blood cells (RBC) among Kuwaiti population. <i>Materials and Methods:</i> Retrospective analysis of RBC alloimmunization among 179,045 Kuwaiti patients, pregnant women, and allogeneic blood donors was conducted for the period of 1992–2001. The frequency of 24 alloantibody specificities from 1,278 alloimmunized Kuwaitis was estimated. <i>Results:</i> The prevalence of positive antibody screen in Kuwait was 0.49%.The five most frequently identified alloantibodies were anti-D (27.3%), anti-E (18.5%), anti-K (15.6%), anti-Le^a (8.7%), and anti-Le^b (6.6%). Frequency of alloimmunization was greater among Kuwaiti female than male patients (3.2 F to 1 M). Anti-D (p < 0.001), anti-E (p = 0.05), anti-K (p = 0.04) were also more frequently identified alloantibody among Kuwaiti females. <i>Conclusion:</i> The results show higher predominance of RBC alloimmunization in females than males. Anti-D, anti-E, and anti-K were the most common clinically significant alloantibodies identified in the Kuwaiti population and were also more frequent among Kuwaiti females.