Three antisera are reported that reacted with all cells tested except the donor’s own and those from K(0) people. Each serum reacted with the cells of the other two donors. The nature of the association of the three antibodies with the Kell system remains unknown.

A French-Canadian En(a- ) propositus, whose red cells are phenotypically like the three previously reported, differs in the mode of reaction of this antibody which is apparently not immune. His consanguineous parents and 2 of this 4 sibs are heterozygous En^a En, the other 2 being En^a En^a. Sialic acid levels and the MN glycoprotein content of the red cells of the family and the PAS-stained patterns of the red cell membranes of the propositus confirm the serological findings.