Objective To evaluate the efficacy of olmesartan medoxomil in Chinese patients with mild to moderate essential hypertension using different methods according to ambulatory blood pressure monitoring. Methods Chinese patients 18-75 years of age with clinic diastolic blood pressure (BP) 90-109 mmHg and systolic BP less than 180 mmHg were treated with olmesartan medoxomil 20-40 mg once daily for 24 weeks to reach the goal BP (<140/90 and <130/80 mmHg in diabetes) in a multicenter study. The trough-to-peak ratio (T/P ratio) and the smoothness index (SI) for systolic/diastolic BP were calculated using different methods according to ambulatory blood pressure monitoring. Result Olmesartan medoxomil 20-40 mg once daily reduced the systolic/diastolic ambulatory BP for 24-h, daytime, and night-time by 13.3 +/- 16.3/7.6 +/- 9.5, 13.9 +/- 17.4/8.0 +/- 10.4, and 12.3 +/- 18.1/6.8 +/- 10.2 mmHg in all eligible patients at week 24 from baseline (n=87, P<0.0001). The global and individual T/P ratios were 0.64/0.62 and 0.32/0.30 (n=87) for systolic/diastolic BP, whereas these were 0.71/0.70 and 0.31/0.39 in fair responders (n=71). Global and individual SI were 6.81/5.37 and 0.92/0.67 (n=87) for systolic/diastolic BP, whereas these were 7.04/5.44 and 1.03/1.03 in fair responders (n=71). Global and individual T/P ratios for systolic/diastolic BP were 0.75/0.82 and 0.45/0.46 in the 20 mg subgroup (n = 41), whereas these were 0.44/0.59 and 0.30/0.29 in the 40 mg subgroup (n=30). Global and individual SI were 5.70/5.32 and 1.03/0.87 for systolic/diastolic BP in the 20 mg subgroup (n = 41), but these were 3.64/2.46 and 1.01/0.60 in the 40 mg subgroup (n=30). Conclusion The duration of the antihypertensive action of olmesartan medoxomil with 20-40 mg once daily can be assessed by the global T/P ratio and SI rather than the individual values, even in different populations and dosages. Blood Press Monit 17: 193-197 (C) 2012 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.