The objective of this study was to analyze predisposing factors of Preeclampsia at Rajavitee Hospital. The retrospective study consisted of 119 total cases and 237 systematic random sampling controls. The data was collected by interviewing patients and recording from doctors diagnosis. By using univariate analysis to estimate Relative Odds of each factors, the results shown that the most important factor was history of hypertension with Relative Odds 13.18. The other risk factors were body mass index, hematocrit level, history of Migrane, maternal weight gain, age, unregistered marriage, rest and primiparity. These factors had RO equal 5.13, 3.56, 3.17, 2.42, 2.29, 1.95, 1.78 and 1.77 respectively. The estimation of Relative Odds when using multivariate analysis indicated that factors predisposing to Preeclampsia were history of hypertension, body mass index, hematocrit level, age, maternal weight gain, history of Migrane, primiparity and unregistered marriage. These factors had RO equal 12.29, 8.79, 4.82, 3.76, 3.55, 3.19, 2.37 and 2.22 respectively.