Improvements in drug-eluting stent design have led to a reduced frequency of repeat revascularisation and new biodegradable polymer coatings may allow a shorter duration of dual antiplatelet therapy (DAPT) after percutaneous coronary intervention (PCI).The Improved Drug-Eluting stent for All-comers Left Main (IDEAL-LM) study aims to investigate long-term clinical outcomes after implantation of a biodegradable polymer platinum-chromium everolimus-eluting stent (BP-PtCr-EES) followed by 4 months DAPT compared to a durable polymer cobalt-chromium everolimus-eluting stent (DP-CoCr-EES) followed by 12 months DAPT in patients undergoing PCI of unprotected left main coronary artery (LMCA) disease.This is a multicentre randomised clinical trial study in patients with an indication for coronary artery revascularisation who have been accepted for PCI for LMCA disease after Heart Team consultation. Patients were randomly assigned in a 1:1 ratio to receive either the BP-PtCr-EES or the DP-CoCr-EES. The primary endpoint was a non-inferiority comparison of the rate of major adverse cardiovascular events (MACE), defined as all-cause death, myocardial infarction, or ischaemia-driven target vessel revascularisation at 2 years.Between December 2014 and October 2016, 818 patients (410 BP-PtCr-EES and 408 DP-CoCr-EES) were enrolled at 29 centres in Europe. At 2 years, the primary endpoint of MACE occurred in 59 patients (14.6%) in the BP-PtCr-EES group and 45 patients (11.4%) in the DP-CoCr-EES group; 1-sided upper 95% confidence interval (CI) 7.18%; p=0.04 for non-inferiority; p=0.17 for superiority. The secondary endpoint event of BARC 3 or 5 bleeding occurred in 11 patients (2.7%) in the BP-PtCr-EES group and 2 patients (0.5%) in the DP-CoCr-EES group (p=0.02).In patients undergoing PCI of LMCA disease, after two years of follow-up, the use of a BP-PtCr-EES with 4 months of DAPT was non-inferior to a DP-CoCr-EES with 12 months of DAPT with respect to the composite endpoint of all-cause death, myocardial infarction or ischaemia-driven target vessel revascularisation.