For the Rhesus categories DIV, DVI, and DVII, agglutination was compared to the number of RHD antigens per cell. We detected 3,100 to 15,400 antigens/cell on DVI. We report examples of anti-D reactivity showing lack of specificity and pointing to the known serologic split in DIV and DVI. Such a split was not found in DVII. Other examples were explained by lack of sensitivity. These results emphasized the need to consider RHD antigen densities, before a serologic split in RHD variant cells is postulated. In this context, flow cytometry may be superior to agglutination titers to determine antigen densities.