Since the recognition that L-arginine (LA) is the natural metabolic donor of nitric oxide, this amino acid has reached the medical spotlight. LA exerts favorable effects in the prevention and treatment of endothelial damage and the restoration of endothelial function in patients with cardiovascular risk factors (hypercholesterolemia, smoking, hypertension, diabetes and advanced age) or with several chronic cardiovascular disorders (coronary, peripheral and cerebral vascular disease, and mild-to-moderate heart failure). LA administration is likely to represent a potentially novel therapeutic strategy during angioplasty, coronary bypass grafting and cardiac transplantation. More conclusive research findings for the rediscovered role of this well-known substance merit close attention.