Background: The Kell blood group system (KBGS) is complex and contains many blood group antigens; these antigens are considered highly immunogenic. KBGS antigens are the third most potent, after the ABO and Rh blood group antigens.

Aims: The aim of this study is to provide essential data about the distribution of the major Kell antigens and the most common phenotype among the Saudi population. Methodology: This is a retrospective study to evaluate the Kell antigens grouping performed among some donors who donated blood or blood products at department of donation center in King Abdulaziz Medical City, Riyadh, Saudi Arabia from 1 st January 2015 to 31 th December 2015. Sample size included four hundred donors. All donors are males and their ages were above 18 years. Results: The Incidence of other kell antigens ie K, k, Kp a and Kp b were 18.2%, 97.0%, 11.7% and 96.0% respectively The most common kell phenotype according to K and k antigens among Saudi donors was K-k+(81.5%) followed by K+ k+(15.5%) followed by K+ k-(3%) and the Kk-phenotype was (0%), while the most common kell phenotype according to Kp a and Kp b antigens among Saudi donors was Kp a-Kp b+(88.0%) followed by Kp a+ Kp b+(7.8%) followed by Kp a+ Kp b-(4.2%) and the Kp a-Kp b-phenotype was (0%). Conclusion: This study showed that there is a wide racial and geographical variation in the distribution of Kell antigens and phenotypes among study participants. The Kell blood group system has vital role in population genetic study and in resolving medical-legal issues and more importantly in transfusion medicine practice.