Objective: To evaluate hypertensive pregnant women by 24-h ambulatory blood pressure monitoring (ABPM) and to compare results with those obtained at the office. Methods: The study population consisted of 17 women with preeclampsia (PE), 15 with mild chronic hypertension (CH), and a control group of 15 normotensive pregnant women. All the patients were evaluated by 24-h ABPM during the third trimester of pregnancy. Results: Diastolic blood pressure (DBP) measured by daytime ABPM in patients with PE or CH was significantly lower than that measured at the office. In each group, the mean values of nighttime ABPM were significantly lower than the mean of daytime office measurements. In the PE group, a significant decline in systolic blood pressure (SBP) and DBP evaluated by nighttime ABPM was observed. In CH, the decline was significantly smaller and less pronounced than in PE. Conclusion: 24-h ABPM appears to be a promising method for the evaluation of hypertensive disorders of pregnancy.