Restenosis is the main limitation of percutaneous transluminal coronary angioplasty (PTCA). It occurs exclusively within the first 6 months after successful PTCA and leads in 25 to 30% of the cases to repeat revascularization. Its pathophysiology appears to involve mainly intimal hyperplasia at the injury site and constrictive remodeling of the whole artery; the relative roles of each remain debated. Detection of restenosis is often simple, when typical angina recurs after a symptom-free interval, but is often enhanced by a stress test, sometimes coupled to a thallium scintigraphy. The value of these tests is enhanced when a pre-PTCA test is available for comparison. The only preventive treatment with proven efficacy is the placement of stents, which however do not provide full protection against the development of restenosis, which suggests that ideal prevention should combine a mechanical approach, targeted against vessel remodeling and a biological approach targeted against intimal hyperplasia.