Hypertension in pregnancy is development of elevated blood pressure of 140/90mmHg or higher after 20 weeks gestation taken on 2 occasions at least six hours apart in a woman who was previously normotensive.1,2,3 Hypertensive disorders in pregnancy ranked among the leading causes of maternal morbidity and mortality.4 Hypertension complicates approximately 10-20% of all pregnancies worldwide and preeclampsia and eclampsia are major causes of maternal and perinatal morbidity and mortality.5 Preeclampsia is defined as systolic blood pressure(BP) level of 140mmHg or higher and diastolic blood pressure of 90mmHg or higher measured at two different occasions of at least six hours apart, occurring after 20 weeks of gestation with proteinuria to the extent of >0.3gm in 24hrs urine specimen. Each year up to 40,000 women mostly in developing countries die of hypertensive disorders.6 Despite the volume of knowledge on hypertension in pregnancy, no preventive measure has been successfully identified. Though the aetiology of preeclampsia is obscured, recent studies have shown that plasma level of calcium may have a role to play in its occurrence. Magnesium supplementation has been suggested without appreciable success especially in African women.7, 8 AIM The study was aimed at determining plasma calcium level as both a prognosticative and predictive factor in disease progression in patients with preeclampsia. OBJECTIVES The objectives of this study were to determine plasma calcium level among pregnant women with preeclampsia and normotensive pregnant women, determine the proportion of cases and control who have hypocalcaemia and to compare plasma calcium level to the degree of hypertension and proteinuria in pre eclamptic patients. METHODOLOGY The study was a prospective case-controlled study of antenatal women who developed preeclampsia while attending the clinic and their control group of corresponding age, estimated gestational age, parity and tribe. Plasma calcium level samples were collected at recruitment and their clinical characteristics were used to generate a database for analysis. Data obtained were entered into the SPSS version 20 software and analyzed using same. Comparison of plasma calcium level values between the cases and controls was done by Independent T test. Simple linear regression to establish for correlation of the calcium levels, protein and blood pressure values among the study groups were carried out. A p-value of <0.05 was considered as statistically significant. 104 patients that fulfilled the inclusion criteria were included, 52 each into preeclamptic group and control group. Ethical approval was obtained for the study from the Research and Ethics committee of Ladoke Akintola University of Technology Teaching Hospital Osogbo, Osun State.