Full HLA-A, B and DR types were obtained for 22 families (mothers, fathers and neonates) associated with severe (proteinuric) pre-eclampsia, 21 families associated with mild pre-eclampsia, and 132 families associated with normal pregnancies. There was an increased frequency of DR4 (relative risk 3.6: p less than 0.003, uncorrected) in both neonates and mothers of the severe pre-eclampsia families when compared to the normotensive controls. There were no significant differences between either pre-eclampsia group and controls in HLA antigen homozygosity, HLA antigen sharing or in lymphocytotoxin production.