Using clinical, morphological, genetic, and biochemical criteria, we studied ten white and North African families with hereditary elliptocytosis (HE). In four families, elliptocytic individuals displayed a highly significant reduction of band 4.1, which was recorded using two electrophoretic procedures. The 4.1a/4.1b ratio was also significantly reduced, as is usually observed in suspensions enriched in young red cells. This form of HE was invariably associated with the following characteristics: absence of clinical signs; numerous, smooth and well-elongated elliptocytes; dominant transmission; and, when investigated, normal osmotic fragility. Its frequency, among all forms of HE, is about one third as a first estimate, at least in whites and North Africans. In the other six families studied, elliptocytic subjects presented normal 4.1 bands. Again, the 4.1a/4.1b ratio was decreased, reflecting the red cell age- dependent changes in these two components. In three of these families, elliptocytosis was accompanied by clinical signs of variable intensity, and the mode of inheritance could not be unequivocally determined. Therefore, HE with a partially reduced band 4.1 defines a homogeneous variety of HE that can be isolated from other forms of HE. We suggest that it be termed the 4.1 (-) trait, so as to correspond with a previously proposed terminology.