To determine whether an association exists between hypertension in pregnancy and later development of cardiovascular disease. Case-control study of women who delivered with and without hypertensive complications during the same period. University Hospital in Reykjavik, Iceland. Three hundred and twenty-five women with hypertension in pregnancy (blood pressure > or =140/90 mmHg after 20 weeks of gestation) in the years 1931-1947, graded by severity. For each case, two normotensive control women, delivering before or after the case and matched for parity and age were selected, giving a total of 629 women. Causes of death were evaluated for the presence of ischaemic heart disease, cerebrovascular events and cancer, up until the end of 1996. Survival curves, median survival times, risk of death by age group and severity of disease. Death with evidence of ischaemic heart disease was more common in cases (24.3%) than in control women (14.6%) (RR 1.66; 95% CI 1.27-2.17). Cerebrovascular event deaths occurred in 9.5% of cases and in 6.5% of controls (RR 1.46; 95% CI 0.94-2.28). Cancer death rates were not different (RR 1.22; 95% CI 0.91-1.63). Survival times were shorter on average by three to nine years as a consequence of cardiovascular disease. This varied by age group in the index pregnancy for women with a history of hypertension in pregnancy. The effect was smaller if the case pregnancy occurred at a young age. There was a linear trend with increasing severity of hypertensive disease in pregnancy in death rates from ischaemic heart disease (chi(2) (1)= 5.8, P= 0.02). Long term follow up suggests an increased risk of death from ischaemic heart disease and cerebrovascular events among women who suffered hypertension in pregnancy.