The efficacy of amlodipine, a long half-life dihydropyridine calcium antagonist, at the dosage of 5-10 mg/day in a single daily administration, has been compared with that of nifedipine R, a short half-life dihydropyridine, at the dosage of 20-40 mg b.i.d. in 29 patients with chronic ischemic heart disease. After a one week placebo period, patients were assigned to the treatment with amlodipine or nifedipine R, according to a randomized sequence and a cross-over, single-blind design, for two control periods of four weeks and without a wash-out interval between these two phases. During the stress test, a significant increase from baseline in test duration and in time to onset of ischemia and of angina have been obtained with both treatments; moreover amlodipine increased significantly the time to onset of ST segment deviation (-1 mm) and the time to maximum ST segment deviation compared with nifedipine R changes. Also with Holter monitoring and in the angina diary there was a significant reduction of anginal episodes. As regards safety profile, amlodipine treatment was associated with a significantly lower incidence of side effects compared with nifedipine R. This is probably due to the particular pharmacokinetics of amlodipine which, besides the long half-life which allows a single daily administration, shows a retarded peak (between the 6th and the 12th hour) with consequent reduction of phenomena connected with fast and excessive peripheral vasodilatation. In conclusion, amlodipine was as effective in reducing the signs of ischemia as nifedipine R, but compliance was better due to the single daily administration and so was tolerability.