OBJECTIVE To examine the efficacy of magnesium sulfate (MgSO4) as an anticonvulsant in eclampsia and imminent eclampsia. METHODS Case records of 562 consecutive patients with eclampsia and 174 with imminent eclampsia treated at the Institute of Obstetrics and Gynaecology, Hyderabad, India, during the 3-year period from January 1987 to December 1989, were reviewed. Management consisted of: (1) MgSO4 to control convulsions; (2) sublingual nifedipine to control hypertension; and (3) delivery of the fetus. RESULTS Convulsions were controlled in 95% of cases with the initial dose of magnesium and within half an hour in a further 2%. Cesarean section was performed mainly for obstetric indications. Depression of knee jerks was found to be the first sign of impending magnesium toxicity and with the precautions observed, magnesium toxicity was negligible. Maternal mortality was 2.4% (18 maternal deaths) and perinatal mortality 36% (247 perinatal deaths). Sixteen women with eclampsia (2.8%) and two with imminent eclampsia (1.1%) died. Of the 247 perinatal deaths, 61 were in the category of imminent eclampsia. There were 10 sets of twins. Cerebrovascular accident was the leading cause of maternal death. Fetal deaths and prematurity were important causes of perinatal loss. CONCLUSIONS The control of convulsions is the most important aspect in the management of eclampsia, and MgSO4 is a very effective anticonvulsant.