Summary. A total population of pregnant women from Aberdeen City District 1967–1978 has been studied. There were 29 851 pregnancies and 6637 women had a first recorded pregnancy between 1967 and 1978 and had two or more pregnancy events. As expected the incidence of pre-eclampsia in a second pregnancy was less than that in a first pregnancy, but it was dependent on the outcome of the first pregnancy. If the first pregnancy was complicated by proteinuric pre-eclampsia than the incidence of the condition in the second pregnancy was similar t o that in a first pregnancy, but women who were normotensive in the first pregnancy had a reduced incidence of the condition in the second pregnancy. The incidence of proteinuric pre-eclampsia after early abortion <13 weeks), either spontaneous or induced was similar to the population incidence in a first pregnancy, but after a late spontaneous abortion the risk of proteinuric pre-eclampsia was significantly reduced. Change of civil status of the offspring from first to second pregnancy did not affect the incidence of pre-eclampsia in a second pregnancy. There was an effect of birthweight in that women who had proteinuric pre-eclampsia in conjunction with a low-birthweight baby (<2500g) in their first pregnancy had double the incidence of proteinuric pre-eclampsia in their second pregnancy. Only a pregnancy of 37 weeks or more is likely to offer protection or ‘immunity’ to pre-eclampsia in a second pregnancy and even then the effect is moderated by the development of pre-eclampsia in the first pregnancy.