The objectives of this double-blind, multicenter, randomized, parallel-arm, placebo-controlled study were to evaluate the dose-related efficacy, tolerability, and safety of candesartan cilexetil, a potent, AT1 selective, long-acting angiotensin II receptor blocker, in 365 adult patients with systemic hypertension and mean sitting diastolic blood pressure (BP) of 95 to 114 mm Hg. Patients received either placebo or candesartan cilexetil 2, 4, 8, 16, or 32 mg once daily for 8 weeks. All doses of candesartan cilexetil reduced trough (24 hours after treatment) sitting diastolic and systolic BP significantly compared with placebo (p < 0.005). A significant (p < or = 0.0001) dose response was evident, with greater decreases in BP at higher doses. Mean changes in BP were -10.7/-7.8 mm Hg and -12.6/-10.2 mm Hg in the 16- and 32-mg groups, respectively, versus -0.3/-2.6 mm Hg in the placebo group. The 16- and 32-mg doses were consistently significantly superior to placebo in antihypertensive effect with regard to all BP measurements, including peak (6 hours after treatment), trough, sitting, and standing measurements of diastolic and systolic BP. Responder rates (trough sitting diastolic BP < 90 or > or = 10 mm Hg BP decrease) were 54% and 64% for the 16- and 32-mg groups, respectively. Tolerability and safety profiles were similar to placebo at all doses. In conclusion, candesartan cilexetil administered once daily effectively reduces BP in a dose-related manner while maintaining safety and tolerability; doses of 16 and 32 mg are most effective for treatment of hypertension.