Azilsartan is a novel angiotensin receptor blocker being developed for hypertension treatment. This 16-week, multicenter, randomized, double-blind study compared the efficacy and safety of azilsartan (20-40 mg once daily by forced titration) and its ability to provide 24-h blood pressure (BP) control, with that of candesartan cilexetil (candesartan; 8-12 mg once daily by forced titration) in 622 Japanese patients with grade I-II essential hypertension. Efficacy was evaluated by clinic-measured sitting BP, and by ambulatory BP monitoring (ABPM) at week 14. Participants (mean age: 57 years, 61% males) had a mean baseline sitting BP of 159.8/100.4 mm Hg. The mean change from baseline in sitting diastolic BP at week 16 (primary endpoint) was -12.4 mm Hg in the azilsartan group and -9.8 mm Hg in the candesartan group, demonstrating a statistically significant greater reduction with azilsartan vs. candesartan (difference: -2.6 mm Hg, 95% confidence interval (CI): -4.08 to -1.22 mm Hg, P=0.0003). The week 16 (secondary endpoint) mean change from baseline in sitting systolic BP was -21.8 mm Hg and -17.5 mm Hg, respectively, a significant decrease with azilsartan vs. candesartan (difference: -4.4 mm Hg, 95% CI: -6.53 to -2.20 mm Hg, P<0.0001). On ABPM, the week 14 mean changes from baseline in diastolic and systolic BP were also significantly greater with azilsartan over a 24-h period, and during the daytime, night-time and early morning. Safety and tolerability were similar among the two groups. These data demonstrate that once-daily azilsartan provides a more potent 24-h sustained antihypertensive effect than that of candesartan but with equivalent safety.