A 90-day, multicenter, randomized, double-blind, parallel-group study was conducted to compare the efficacy of amlodipine (once a day) with nicardipine (two to three times a day), in the treatment of isolated systolic hypertension (ISH) in the elderly. Patients (n = 133) aged > or = 60 years, with ISH were randomized to receive either amlodipine 5 mg/day, or nicardipine 60 mg/day (titrated if necessary to 10 mg/day and 100 mg/day, respectively) for 90 days. Efficacy was assessed by measuring office blood pressure (BP), and 24-h ambulatory blood pressure monitoring (ABPM). The two treatments substantially and comparably reduced office systolic blood pressure (SBP) and pulse pressure (PP), and also produced a slight decrease in diastolic blood pressure (DBP). Amlodipine reduced SBP, as assessed by ABPM, to a significantly greater extent than nicardipine. Both treatments were well-tolerated. The sustained effect of amlodipine, compared with nicardipine, was reflected in its significantly greater antihypertensive activity, particularly during the nocturnal period, as assessed by ABPM. The study demonstrates that once a day dose of amlodipine is an effective antihypertensive treatment for elderly ISH patients.