 4. Objective: The primary objective of this study is to test the hypothesis that amlodipine compared with nifedipine GITS has a stronger effect in preventing morning blood pressure surge 4 am to 8 am in mild to moderate hypertensive patients.The secondary objective of the study is to compare the effects of amlodipine and nifedipine GITS in reducing nighttime blood pressure 10 pm to 4 am in patients with a decreased nocturnal blood pressure fall. 