The antihypertensive efficacy and safety of amlodipine was evaluated in an open, multicenter general practice study. Hypertensive patients with sitting diastolic blood pressure in the range 95-115 mm Hg entered an initial 2-week baseline period during which they received placebo in a single-blind fashion. The dose of any concomitant antihypertensive treatment was kept constant for 4 weeks prior to baseline evaluations and throughout the study. Patients with an average sitting diastolic blood pressure > or = 95 mm Hg and < or = 115 mm Hg at two consecutive visits during the baseline period continued to the 8-week dose adjustment phase of the study. Patients were started on 5 mg of amlodipine once daily adjusted after 4 weeks to 10 mg once daily to achieve a target sitting diastolic blood pressure < or = 90 mm Hg. Amlodipine treatment produced significant falls in blood pressure (-23.7/-17.3 mm Hg; p < 0.05) with no effect on heart rate. Amlodipine was well tolerated, with most adverse events being mild or moderate. Investigators' global evaluation of toleration was excellent or good in 92% of patients. Subgroup analysis showed amlodipine to be equally efficacious and well tolerated in elderly or young patients, and in patients taking amlodipine as monotherapy or combination therapy.