This study aimed to assess the incidence of eclampsia in the United Kingdom and its associated morbidity and mortality. A prospective, descriptive study was conducted to collect data on all cases of eclampsia in the UK in 1992. Information was gathered from hospital case notes and questionnaires sent to general practitioners. The study included 383 confirmed cases of eclampsia, with an incidence rate of 4-9 per 10,000 maternities. Most convulsions occurred despite antenatal care, and many occurred within one week of the woman's last visit to a doctor or midwife. Three quarters of first seizures occurred in hospital, with 38% developing before both proteinuria and hypertension were documented. Forty four percent of cases occurred postpartum, more than a third antepartum, and the remainder intrapartum. Nearly one in 50 women (1·8%) died, and 35% of all women had at least one major complication. The rate of stillbirths and neonatal deaths was 22·2/1000 and 34·1/1000, respectively. Preterm eclampsia was more common antepartum and was associated with more maternal complications and fetuses that were small for gestational age. Antepartum eclampsia was more likely to occur preterm and was associated with higher maternal complications and neonatal mortality. Both factors contributed independently to the severity of the outcome. Eclampsia occurs in nearly one in 2000 maternities in the UK and is associated with high maternal morbidity and fatality. It may present unheralded by warning signs. Preterm and antenatal eclampsia seem to be particularly severe. The study also found that eclampsia often occurred despite normal antenatal care and was not always preceded by hypertension and proteinuria. The findings suggest that further research is needed to develop new screening and diagnostic tests for features other than hypertension and proteinuria to reduce the incidence of eclampsia. The study was funded by the medical audit unit of the Royal College of Obstetricians and Gynaecologists.This study aimed to assess the incidence of eclampsia in the United Kingdom and its associated morbidity and mortality. A prospective, descriptive study was conducted to collect data on all cases of eclampsia in the UK in 1992. Information was gathered from hospital case notes and questionnaires sent to general practitioners. The study included 383 confirmed cases of eclampsia, with an incidence rate of 4-9 per 10,000 maternities. Most convulsions occurred despite antenatal care, and many occurred within one week of the woman's last visit to a doctor or midwife. Three quarters of first seizures occurred in hospital, with 38% developing before both proteinuria and hypertension were documented. Forty four percent of cases occurred postpartum, more than a third antepartum, and the remainder intrapartum. Nearly one in 50 women (1·8%) died, and 35% of all women had at least one major complication. The rate of stillbirths and neonatal deaths was 22·2/1000 and 34·1/1000, respectively. Preterm eclampsia was more common antepartum and was associated with more maternal complications and fetuses that were small for gestational age. Antepartum eclampsia was more likely to occur preterm and was associated with higher maternal complications and neonatal mortality. Both factors contributed independently to the severity of the outcome. Eclampsia occurs in nearly one in 2000 maternities in the UK and is associated with high maternal morbidity and fatality. It may present unheralded by warning signs. Preterm and antenatal eclampsia seem to be particularly severe. The study also found that eclampsia often occurred despite normal antenatal care and was not always preceded by hypertension and proteinuria. The findings suggest that further research is needed to develop new screening and diagnostic tests for features other than hypertension and proteinuria to reduce the incidence of eclampsia. The study was funded by the medical audit unit of the Royal College of Obstetricians and Gynaecologists.