SUMMARY A retrospective survey was made of the pregnancies of 78 women whose sera had been shown to contain leucocytotoxic antibodies during pregnancy. The incidence of preeclamptic toxaemia in this group was compared with the incidence in a control group in whom such antibodies were not demonstrated. The incidence of preeclamptic toxaemia in the two groups was not significantly different. These results suggest that leucocytotoxic antibodies to foetal antigens are not important in the genesis of preeclampsia and that screening pregnant women for such antibodies is of no value in detecting those at risk from this complication.