83 patients were enrolled in a multicentre, randomized, open study to assess the efficacy of amlodipine in stable effort angina. Preselected patients were submitted to a one-week placebo wash-out period during which only nitrates or molsidomine were authorized. Patients were then randomized to receive either 5 mg of amlodipine as a morning dose, or 180 mg of diltiazem in three divided doses. After two weeks, the dosage was able to be increased (according to clinical efficacy) to 10 mg of amlodipine as a single dose or 240 mg of diltiazem in four divided doses. The antianginal efficacy of these two treatments was essentially evaluated in terms of the results of stress tests (ST) conducted at the end of the second week and fourth week of active treatment: and 24 hours after the last dose of the drug. The results of 63 patients who scrupulously complied with the protocol showed that amlodipine and diltiazem corrected or improved the ST parameters (time to onset and amplitude of ST depression, duration of ST, work performed). The anti-ischaemic action of amlodipine was maintained for at least 24 hours after the last dose and therefore provides better security (by covering the entire 24-hour period) and better compliance (by tolerating a dose omission of several hours).