The haemoglobin, haematocrit and osmotic fragility red cell values in a South African white woman with Rhnull cells and the corresponding haematological syndrome were shown to vary only minimally during her third pregnancy. This occurred in spite of the precautionary donation by her of two units of her blood at 20 and 27 weeks of pregnancy for storage in liquid nitrogen. Although there was fear to the contrary, the woman's infant was found at birth to be suffering only mildly from haemolytic disease of the newborn due to the anti-Rh29 antibodies present in her plasma.