In a healthy 32-yr-old woman with normal red cell morphology, a shortened variant of cytoskeletal membrane protein 4.1 is described at the heterozygous state. One haploid set of protein 4.1 migrates below protein 4.2 and displays a reduction in mass of approximately 8500 with regard to the normal haploid set. The shortening corresponds to a deletion of about 75 amino acids and concerns both subcomponents a and b of protein 4.1. It seems to involve some phosphorylation site(s). It was transmitted to the proposita's son (who inherited elliptocytosis with band 4.1 deficiency from his father). To our knowledge, the present abnormality is the first unequivocal variant of erythrocyte membrane protein 4.1 recognized up to now.