A randomized, double-blind, placebo-controlled study in patients with clinical symptoms of stable angina pectoris and healed myocardial infarction (n = 22) has shown that oral supplementation with L-arginine (6 g/day for 3 days) increases exercise capacity (tested on a Marquette case 12 treadmill according to the modified Bruce protocol). Results suggest that the inefficient L-arginine/nitric oxide system contributes to limitation of myocardial perfusion and/or peripheral vasodilation during maximum exercise in patients with stable angina pectoris.