The aim of this study was to determine the efficacies of valsartan and telmisartan as add-on agents for the control of morning blood pressure (BP) in patients already on amlodipine monotherapy. A total of 414 hypertensive patients were prospectively enrolled in a 4-week run-in period when they were treated with amlodipine (5 mg/day), and home BP was measured in the morning and evening. Patients with home systolic BP (SBP) being 135-159 mm Hg in the morning at the end of the run-in period were randomized to additional treatment with valsartan (80 mg/day) or with telmisartan (40 mg/day) for 8 weeks. The primary endpoint was the change in morning home BP, and secondary endpoints included variability of morning home BP. Of the 282 patients randomized, 262 patients (n=131, in each treatment) completed the protocols. Demographic parameters and baseline morning SBP/diastolic BP (DBP) (146.3±7.1/84.8±9.3 vs. 146.0±7.1/84.2±9.1 mm Hg) were comparable in the valsartan group and telmisartan group, and changes in SBP/DBP after 8-week treatment were not significantly different between the two groups (-7.4±10.6/-3.9±6.1 vs. -8.3±9.9/-5.0±5.9 mm Hg). Valsartan significantly increased individual standard deviation and variation coefficient of morning SBP, but telmisartan did not change either of these indices of SBP variation. In subgroups with baseline SBP being above the median (145.2 mm Hg), change in DBP was significantly larger by telmisartan than by valsartan (-6.3±5.6 vs. -3.9±6.7 mm Hg, P<0.05). These results suggest that telmisartan is more useful than valsartan as an add-on agent for reducing the level and variability of morning BP in patients on amlodipine monotherapy.