 3. Rationale: Several recent studies compared 24-h blood pressure lowering effect of these 2 dihydropyridine drugs, amlodipine and nifedipine GITS, but produced inconsistent results. Therefore, a randomized controlled trial with a larger sample size is required to compare these 2 dihydropyridines in the blood pressure control over 24 hours in general and during early morning hours and at night in particular. 