Background: Worldwide, pre-eclampsia and eclampsia contribute to the death of a pregnant woman every three minutes. Aim: To determine the demographic risk factors and values of blood pressure to predict preeclampsia. Material and Methods: Demographic and clinical features of 300 normotensive pregnant women aged 28 +/- 5 years and 100 preeclamptic women aged 28 +/- 6 years, were assessed. Women with multiple pregnancies were excluded from the study. Results: Women with less educational attainment had a higher risk of mild and severe preeclampsia. Weight gain during pregnancy in control and pre eclamptic women were 14 +/- 3 and 20 +/- 5 kg, respectively (p < 0.01). Women with severe preeclampsia had high significantly shorter gestations then the other two patient groups (p < 0.01). Compared to normotensive women, at 6 to 12 weeks of gestation, pre eclamptic women had higher systolic (102 +/- 7 and 113 +/- 9 mmHg respectively), diastolic ( 64 +/- 5 and 74 +/- 10 mmHg respectively) and mean arterial pressure (77 +/- 5 and 87 +/- 8.01 mmHg respectively). Conclusions: Women with basic education or illiterate have a higher risk of developing preeclampsia. During the first or second trimester of pregnancy, mean arterial pressure is the best predictor for preeclampsia. (Rev Med Chile 2010; 139: 748-754).