An antibody to a high frequency antigen, made in a WES+ Black antenatal patient (Wash.), failed to react with the red cells of a presumed WES^+ homozygote and is, therefore, probably antithetical to anti-WES. Like anti-WES, it reacted with papain, ficin, trypsin or neuraminidase treated cells but not with α-chymotrypsin or pronase treated cells and was specifically inhibited by concentrated serum. It also reacted more strongly in titration with WES- cells than with WES+ cells. The antibody is Cromer-related as it failed to react with Inab phenotype (IFC-) cells and reacted only weakly with Dr(a-) cells. Wash, cells and those of the other possible WES^+ homozygote are Cr(a+) Tc(a+b-c-) Dr(a+) IFC+ but reacted only very weakly with anti-Es^a.