Percutaneous coronary intervention (PCI) is the dominant method for mechanically improving myocardial perfusion in the treatment of coronary artery disease. The procedure is performed via a small intra-arterial sheath and usually involves a single overnight stay in hospital. Day-case treatment is not infrequent. A balloon is used to dilate the coronary stenosis and a stent is then implanted to scaffold the vessel. Re-narrowing at the treated site may occur but has been greatly reduced by drug-eluting stents. Most acute complications of PCI are mediated by platelet activation, so that drugs blocking platelet aggregation are pivotal to the safety of the procedure. Early complications include haemorrhage from the arterial access site (reduced by a radial approach). Abrupt vessel closure, CVA and tamponade are very rare. The requirement for emergency cardiac surgery is less than 0.1% and in-hospital mortality is mainly determined by the indication for PCI – about 0.2% in those with stable angina, 5% following STEMI and 30% to 50% in the context of cardiogenic shock. Technical advances mean that patients with complex coronary artery disease and co-morbid conditions can now be treated by PCI.