In a series of 26,209 patiens, the incidence of pre-eclampsia was 9.3%, being significantly higher in primiparae (14.1%) than multiparae (5.7%) (P less than 0.001). In patients with early-onset pre-eclampsia there were highly significant (P less than 0.001) increases in the incidences of proteinuria, severe hypertension, placental abruption, fetal growth retardation, neonatal asphyxia and perinatal mortality. There were no significant differences between the incidences of these complications in primiparae and multiparae. The incidence of subnormal oestriol excretion was increased before the emergence of early-onset pre-eclampsia with equal to significance (P less than 0.001) in primiparae and multiparae. Eclampsia was more common in patients with late-onset pre-eclampsia, but not significantly so.