One hundred and fifty-five cord cells were tested for the red blood cell antigens Lua, Lub and Cob in order to collect data on the early postnatal expression of these markers. Additionally, dosage studies were carried out in 8 - 10-month-old heterozygous children. Antigens Lua and Lub revealed to be significantly less expressed in children of both ages compared with those of their mothers, whereas no such differences could be demonstrated in the expression of the antigen Cob.