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Background: The weak RhD phenotype is a form of RhD antigen that, in routine RhD typing, does not react by agglutination with potent monoclonal anti-D serum, but requires addition of antiglobulin serum to demonstrate the presence of the antigen. However, the weak D antigen can cause immunization or sensitization when a truly D-negative recipient is exposed to it. It is therefore crucial to correctly determine the RhD status of units in the blood donor pool of a transfusion service.Statement of the problem: The prevalence of the weak RhD phenotype is known to vary between races and countries, and the documented prevalence in one race or country is not applicable to others. The prevalence of the weak Rh-D phenotype has not been well documented in the Kenya population.Objectives: The objective of the study was to determine the prevalence of the weak RhD antigen in blood donors at the RBTC in Nairobi. The study was also to explore the weak RhD antigen in relation to the gender and age of the donors in the population.Methods: Donor blood samples were typed by mixing monoclonal anti D with red cell saline suspensions in microtitre plates which were then spun at 2000 rpm for 1 minute. RhD negative samples were further tested by a tube agglutination method. Samples confirmed negative by the two methods were then tested by the indirect antiglobulin technique (IAT) in a Du test.Results: Of the 384 donor samples tested, 26 (6.8%) reacted negatively with an􀆟 D in the microtitre and tube tests. Eight (30.8% of negatives, and 2.1 % of total) of the 26 “negative” samples reacted positively by the IAT or Du test. There was no relationship between gender or age and weak RhD positivity.Conclusion and recommendation: The prevalence of weak RhD was found to be 2.1 % in the donor population of the RBTC Nairobi Kenya. The Du test should be applied to all blood donor samples found to be RhD negative in routine blood typing.Keywords: Weak RhD antigen, Du Test, Microtitre, Anti Human Globulin (AHG), Monoclonal anti -D