Objective: To evaluate the efficacy and tolerability of once-daily amlodipine (Pfizer Pharmaceuticals Inc.) alone or in combination with other antihypertensive drugs in an Asian population with essential hypertension. Patients: An open study was undertaken in 165 male and 158 female patients with uncomplicated hypertension (diastolic blood pressure 95 to 115 mm Hg). Patients were recruited from 41 general practices in seven Asian countries and received amlodipine 5 mg daily for 4 weeks and then 10 mg once daily for a further 4 weeks if the target diastolic blood pressure of ≤ 90 mm Hg or a reduction from baseline by ≥ 10 mm Hg had not been achieved. This one-step dose-adjustment period was followed by a 4-week maintenance period on a constant dose. Amlodipine was the sole medication in 284 patients and was added to other antihypertensive drugs in 39 patients uncontrolled on previous medication. Results: 263 patients, including 131 males, were evaluated for efficacy at the final treatment visit. 166 (63%) patients achieved the target reduction in diastolic blood pressure with amlodipine 5 mg once daily, while 84 patients achieved the target reduction with 10 mg once daily. Systolic and diastolic blood pressure reductions were similar irrespective of gender or age, and there were no significant changes in resting heart rate in any subgroup. In 68 patients who underwent ambulatory monitoring, the systolic and diastolic blood pressures were reduced by once-daily amlodipine throughout the 24-hour period without change in the intrinsic circadian pattern. Amlodipine was well tolerated in all patient subgroups; adverse events accounted for less than 1% of treatment discontinuations, and there were no hospitalisations or deaths during the study. Investigators rated both the antihypertensive efficacy and tolerability of amlodipine as excellent or good in 93% of patients. Conclusion: In 263 Asian patients with uncomplicated essential hypertension treated in general practice, once-daily amlodipine in a dose of 5 or 10 mg provided significant antihypertensive efficacy either as monotherapy or in combination with other antihypertensive drugs while maintaining a favourable tolerability profile regardless of gender or age.